After the 9/11 attacks, the public was told al Qaeda acted alone, with no state sponsors.

But the White House never let it see an entire section of Congress’ investigative report on 9/11 dealing with “specific sources of foreign support” for the 19 hijackers, 15 of whom were Saudi nationals.

It was kept secret and remains so today.

President Bush inexplicably censored 28 full pages of the 800-page report. Text isn’t just blacked-out here and there in this critical-yet-missing middle section. The pages are completely blank, except for dotted lines where an estimated 7,200 words once stood (this story by comparison is about 1,000 words).

A pair of lawmakers who recently read the redacted portion say they are “absolutely shocked” at the level of foreign state involvement in the attacks.

Reps. Walter Jones (R-NC) and Stephen Lynch (D-Mass.) can’t reveal the nation identified by it without violating federal law. So they’ve proposed Congress pass a resolution asking President Obama to declassify the entire 2002 report, “Joint Inquiry Into Intelligence Community Activities Before and After the Terrorist Attacks of September 11, 2001.”

Some information already has leaked from the classified section, which is based on both CIA and FBI documents, and it points back to Saudi Arabia, a presumed ally.

The Saudis deny any role in 9/11, but the CIA in one memo reportedly found “incontrovertible evidence” that Saudi government officials — not just wealthy Saudi hardliners, but high-level diplomats and intelligence officers employed by the kingdom — helped the hijackers both financially and logistically. The intelligence files cited in the report directly implicate the Saudi embassy in Washington and consulate in Los Angeles in the attacks, making 9/11 not just an act of terrorism, but an act of war.

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The findings, if confirmed, would back up open-source reporting showing the hijackers had, at a minimum, ties to several Saudi officials and agents while they were preparing for their attacks inside the United States. In fact, they got help from Saudi VIPs from coast to coast:

LOS ANGELES: Saudi consulate official Fahad al-Thumairy allegedly arranged for an advance team to receive two of the Saudi hijackers — Khalid al-Mihdhar and Nawaf al-Hazmi — as they arrived at LAX in 2000. One of the advance men, Omar al-Bayoumi, a suspected Saudi intelligence agent, left the LA consulate and met the hijackers at a local restaurant. (Bayoumi left the United States two months before the attacks, while Thumairy was deported back to Saudi Arabia after 9/11.)

SAN DIEGO: Bayoumi and another suspected Saudi agent, Osama Bassnan, set up essentially a forward operating base in San Diego for the hijackers after leaving LA. They were provided rooms, rent and phones, as well as private meetings with an American al Qaeda cleric who would later become notorious, Anwar al-Awlaki, at a Saudi-funded mosque he ran in a nearby suburb. They were also feted at a welcoming party. (Bassnan also fled the United States just before the attacks.)

WASHINGTON: Then-Saudi Ambassador Prince Bandar and his wife sent checks totaling some $130,000 to Bassnan while he was handling the hijackers. Though the Bandars claim the checks were “welfare” for Bassnan’s supposedly ill wife, the money nonetheless made its way into the hijackers’ hands.

Other al Qaeda funding was traced back to Bandar and his embassy — so much so that by 2004 Riggs Bank of Washington had dropped the Saudis as a client.

The next year, as a number of embassy employees popped up in terror probes, Riyadh recalled Bandar.

“Our investigations contributed to the ambassador’s departure,” an investigator who worked with the Joint Terrorism Task Force in Washington told me, though Bandar says he left for “personal reasons.”

FALLS CHURCH, VA.: In 2001, Awlaki and the San Diego hijackers turned up together again — this time at the Dar al-Hijrah Islamic Center, a Pentagon-area mosque built with funds from the Saudi Embassy. Awlaki was recruited 3,000 miles away to head the mosque. As its imam, Awlaki helped the hijackers, who showed up at his doorstep as if on cue. He tasked a handler to help them acquire apartments and IDs before they attacked the Pentagon.

Awlaki worked closely with the Saudi Embassy. He lectured at a Saudi Islamic think tank in Merrifield, Va., chaired by Bandar. Saudi travel itinerary documents I’ve obtained show he also served as the ­official imam on Saudi Embassy-sponsored trips to Mecca and tours of Saudi holy sites.

Most suspiciously, though, Awlaki fled the United States on a Saudi jet about a year after 9/11.

As I first reported in my book, “Infiltration,” quoting from classified US documents, the Saudi-sponsored cleric was briefly detained at JFK before being released into the custody of a “Saudi representative.” A federal warrant for Awlaki’s arrest had mysteriously been withdrawn the previous day. A US drone killed Awlaki in Yemen in 2011.

HERNDON, VA.: On the eve of the attacks, top Saudi government official Saleh Hussayen checked into the same Marriott Residence Inn near Dulles Airport as three of the Saudi hijackers who targeted the Pentagon. Hussayen had left a nearby hotel to move into the hijackers’ hotel. Did he meet with them? The FBI never found out. They let him go after he “feigned a seizure,” one agent recalled. (Hussayen’s name doesn’t appear in the separate 9/11 Commission Report, which clears the Saudis.)

SARASOTA, FLA.: 9/11 ringleader Mohamed Atta and other hijackers visited a home owned by Esam Ghazzawi, a Saudi adviser to the nephew of King Fahd. FBI agents investigating the connection in 2002 found that visitor logs for the gated community and photos of license tags matched vehicles driven by the hijackers. Just two weeks before the 9/11 attacks, the Saudi luxury home was abandoned. Three cars, including a new Chrysler PT Cruiser, were left in the driveway. Inside, opulent furniture was untouched.

Democrat Bob Graham, the former Florida senator who chaired the Joint Inquiry, has asked the FBI for the Sarasota case files, but can’t get a single, even heavily redacted, page released. He says it’s a “coverup.”

Is the federal government protecting the Saudis? Case agents tell me they were repeatedly called off pursuing 9/11 leads back to the Saudi Embassy, which had curious sway over White House and FBI responses to the attacks.

Just days after Bush met with the Saudi ambassador in the White House, the FBI evacuated from the United States dozens of Saudi officials, as well as Osama bin Laden family members. Bandar made the request for escorts directly to FBI headquarters on Sept. 13, 2001 — just hours after he met with the president. The two old family friends shared cigars on the Truman Balcony while discussing the attacks.

Bill Doyle, who lost his son in the World Trade Center attacks and heads the Coalition of 9/11 Families, calls the suppression of Saudi evidence a “coverup beyond belief.” Last week, he sent out an e-mail to relatives urging them to phone their representatives in Congress to support the resolution and read for themselves the censored 28 pages.

Astonishing as that sounds, few lawmakers in fact have bothered to read the classified section of arguably the most important investigation in US history.

Granted, it’s not easy to do. It took a monthlong letter-writing campaign by Jones and Lynch to convince the House intelligence panel to give them access to the material.

But it’s critical they take the time to read it and pressure the White House to let all Americans read it. This isn’t water under the bridge. The information is still relevant ­today. Pursuing leads further, getting to the bottom of the foreign support, could help head off another 9/11.

As the frustrated Joint Inquiry authors warned, in an overlooked addendum to their heavily redacted 2002 report, “State-sponsored terrorism substantially increases the likelihood of successful and more ­lethal attacks within the United States.”

Their findings must be released, even if they forever change US-Saudi relations. If an oil-rich foreign power was capable of orchestrating simultaneous bulls-eye hits on our centers of commerce and defense a dozen years ago, it may be able to pull off similarly devastating attacks today.

Members of Congress reluctant to read the full report ought to remember that the 9/11 assault missed its fourth target: them.