Families of Sept. 11 victims have been on a 17-year-long quest to seek financial retribution from the Kingdom of Saudi Arabia, which they claim funded the terrorist attack that took the lives of their loved ones. Throughout the process, their attempts at uncovering the truth about Saudi Arabia’s role in the deadliest terrorist attack in American history have been impeded by the FBI and its former director, Robert Mueller — now famously the special counsel investigating collusion (or the lack thereof) between the Trump campaign and the Russian government.

New York-based lawyer Jim Kreindler, representing the families of the Sept. 11 victims, said in an interview with me that Mueller and his successor, James Comey, engaged in a systematic cover-up of evidence that the Saudi government aided the terrorists who committed the Sept. 11 attacks.

Kreindler and the victims’ families believe there are clear connections between the Saudi government and Sept. 11 hijackers Nawaf al-Hazmi and Khalid al-Mihdhar. Both men met with the employees of Saudi Arabia’s Ministry of Islamic Affairs and received support from Saudi diplomat Fahad al-Thumairy, according to a 28-page report on the Saudi links to the Sept. 11 attacks.

Several people formerly associated with the investigation stated that Saudi Arabia was financially involved with the Sept. 11 attacks, including John Lehman , a Republican member of the 9/11 Commission, and former Sen. Bob Graham, D-Fla., who chaired the Senate Select Committee on Intelligence at the time. Graham’s testimony during an appearance on " 60 Minutes" was especially damning: "the hijackers received active support and guidance from rich Saudis, Saudi charities, and top members of the Saudi government.”

Stephen K. Moore, the retired FBI agent who led the Sept. 11 probe in Los Angeles, also confirmed in an affidavit back in December 2017 that the Saudis played a significant role.

Despite mounting evidence and testimony from key players in the investigation as well as former politicians, Kreindler told me that he ran into significant roadblocks from the FBI and former directors Mueller and Comey.

“We’ve really been stymied over the last 17 years from getting information from the FBI, State Department, and Department of Defense,” Kreindler said in an interview. “From day one, instead of focusing on the evidence, there was an effort to not look at the Saudis and get their help in launching the Iraq War.”

Kreindler said that retired FBI agents had told him that they also believe Mueller lied in 2002 before the joint congressional inquiry that he was unaware of Saudi government involvement.

“In [former FBI agent] Steve Moore’s affidavit he says, as head of the 400 FBI agent team in L.A., I am reporting on our investigation into al-Thumairy daily with the director, that’s Director Mueller,” Kreindler stated.

It’s not just Kreindler pointing the finger at Mueller; Graham stated that Mueller personally intervened to cut off further inquiry regarding Saudi assistance to the hijackers in California. In an interview with Harper’s from October 2017, Graham stated that Mueller made a series of objections to having terrorist specialist and former FBI lawyer Michael Jacobson visit San Diego to see if there was a possible Saudi connection to the hijackers. When Jacobson discovered that the hijackers were close to an FBI informant named Abdussattar Shaikh, he demanded to speak to him — but Mueller refused and moved Shaikh to an undisclosed location “for his safety.”

The FBI didn’t become easier to work with once Comey took over. The documents Kreindler requested had heavy redactions, and in 2015 Comey shut down any last remaining FBI investigation into the link between Saudi Arabia and the Sept. 11 attacks.

The Sept. 11 families he’s representing are continuing with their lawsuit, winning a court case in March 2018 where a judge ruled that they can proceed with their lawsuit. Still, Kreindler believes the only way victims’ families will ever learn the whole truth is if President Trump declassifies the investigation into Saudi ties with the Sept. 11 attacks.

“President Trump must declassify all documents related to the 9/11 investigation to fully reveal the significant degree to which Mr. Mueller and later Mr. Comey went to impede and cover up Saudi involvement in the 9/11 attacks,” Kreindler said. “The president should also issue an executive order holding harmless all retired FBI agents who were aware of the cover-up and impediments by their bosses at the time but are afraid to come forward to help the 9/11 victims today out of fear of retribution.”

Ryan Girdusky (@RyanGirdusky) is a contributor to the Washington Examiner's Beltway Confidential blog. He is a writer based in New York.