WASHINGTON — The CIA has videotapes, after all, of interrogations in a secret overseas prison of admitted 9/11 plotter Ramzi Binalshibh.

Discovered in a box under a desk at the CIA, the tapes could reveal how foreign governments aided the United States in holding and interrogating suspects. And they could complicate U.S. efforts to prosecute Binalshibh, 38, who has been described as one of the “key plot facilitators” in the Sept. 11, 2001, attacks.

Apparently the tapes do not show harsh treatment – unlike videos the agency destroyed of the questioning of other suspected terrorists.

The two videotapes and one audiotape are believed to be the only existing recordings made within the prison system.

The tapes depict Binalshibh’s interrogation sessions in 2002 at a Moroccan-run facility the CIA used near Rabat, several current and former U.S. officials said. They spoke on the condition of anonymity because the videos remain a secret.

When the CIA destroyed its cache of 92 videos of two other al-Qaida operatives, Abu Zubaydah and Abd al-Nashiri, being waterboarded in 2005, officials believed they had wiped away all of the agency’s interrogation footage. But in 2007, a staff member discovered a box tucked under a desk in the CIA’s Counterterrorism Center and pulled out the Binalshibh tapes.

If the tapes surfaced at Binalshibh’s trial, they could highlight Morocco’s role in a counterterrorism program that authorized the CIA to hold terrorists in secret prisons and shuttle them to other countries.

The American Civil Liberties Union has asked the government for more information about the tapes as part of a suit involving the treatment of detainees.

“Today’s report is a stark reminder of how much information the government is still withholding about the Bush administration’s interrogation policies,” said Alexander Abdo, staff attorney with the ACLU National Security Project.

More significantly to Binalshibh’s defense, the tapes also could provide evidence of his mental state within the first months of his capture. In court documents, defense lawyers have been asking for medical records to see whether his years in CIA custody made him mentally unstable. He is being treated for schizophrenia with anti-psychotic medications.

With military trial commissions on hold while the Obama administration figures out what to do with a number of terror suspects, Binalshibh has never had a hearing on whether he is mentally fit to stand trial.