Guantanamo Bay , Cuba ( CNN ) -- Lawyers for Khalid Sheik Mohammed and four other prisoners charged in the September 11 attacks say the FBI has questioned more members of the Guantanamo Bay detainees ' defense team than were previously disclosed . That could mean further delays in proceedings against the five accused of plotting the 2001 terrorist attacks . A court is hearing pretrial motions to prepare for the trial of Mohammed , who 's been called the 9/11 mastermind , and the four others . Defense attorneys revealed the new information at a news conference at the U.S. naval base Sunday . Defense lawyers have previously said that the FBI approached one defense security officer , who was asked to become an informant . The U.S. Justice Department has acknowledged the contact and said investigators looked into whether someone on the defense team representing defendant Ramzi bin al-Shibh may have aided unauthorized communication between him and people overseas . The investigation was closed with no charges being brought . Lawyers for the defense team said Sunday that their investigation revealed that the FBI asked three other members of the defense team to cooperate and not to reveal that they were approached . They said a second investigation also has been closed with no charges . Hearings this week at Guantanamo Bay are expected to deal with the FBI investigations to see if there 's a conflict of interest . Defense attorneys said they are preparing new pretrial motions to deal with the fallout from the FBI investigations . `` One of the scenarios is that one or more of the defense teams would have to be replaced , '' said James Connell , an attorney for one of the defendants . That could lead to even more delays in the case going to trial . The four people approached by the FBI had top-secret clearances , working with the defense teams to help them sort through classified information . Three of them worked for a security contracting company based in Washington . CNN 's Evan Perez contributed to this report .
The FBI has questioned more defense team members than thought , lawyers say . Comment: Defense says it 's preparing new pretrial motions to deal with fallout from FBI investigations .