Guantanamo Bay , Cuba ( CNN ) -- A judge needs to decide if new lawyers are needed to defend Khalid Sheikh Mohammed and four other prisoners charged in the September 11 terrorist attacks or if more hearings should be conducted on whether there 's any conflict of interest caused by an FBI investigation . A U.S. Justice Department lawyer acknowledged Monday that the FBI investigated members of the team representing Mohammed and the other Guantanamo Bay detainees accused of the September 11 attacks , prompting the lead defense lawyer to threaten to pull out of the case out of fears that he too is a subject of a federal probe . `` I do have a reasonable fear . I am trimming my sails . I am pulling my punches . I am being extremely careful about how I proceed , '' David Nevel told the military commission hearing the case , adding that he canceled a trip to the Middle East to do investigative work . Defense attorneys argued that the FBI essentially infiltrated and spied on them by asking members of the team if the lawyers were engaged in suspicious activity . The lawyers said in court that two civilian investigators , a classification expert and Mohammed 's linguist were approached by the FBI . The FBI investigation centered on the release of classified information to unknown third parties that are not part of the case . Fernando Campanor-Sanchez , an assistant United States attorney , said the investigations are now closed and that none of the lawyers or anyone else on team are currently under investigation . The four that were under investigation no longer work for the defense team . Undisclosed FBI questions could slow Guantanamo detainee trials .
There could be more hearings on whether an FBI investigation caused a conflict of interest . The FBI questioned four people on defense team , none of them lawyers . They were asked to testify about their knowledge and opinions regarding the case before they would answer questions from congress. Assistant U.S. attorney says no one is currently under investigation .