Bangladesh investigators probing the bloody BDR mutiny said that they have gathered clues that outsiders in uniform took part in the massacre of army officers as BDR personnel claimed "masked" soldiers forced them to join the revolt,reports said on Wednesday. Newly appointed dilapidated BDR chief Brigadier General Mainul Islam told the Daily Star without elaboration that video footage taken during the massacre inside the paramilitary force's headquarters at Pilkhana in Dhaka showed movement of "some unknown people wearing BDR uniforms". Islam could not be reached immediately for comments and army's operations director Brigadier General Ziaul Hassan declined to reconfirm the "outsiders" participation "at this stage" as investigations were still underway. "We have been gathering many information,but I can't confirm of the outsiders took part in the massacre in uniform until we are sure or could catch any of them," he said. Newspaper reports said several BDR soldiers who fled Pilkhana during the mutiny and returned to report back to work said that "masked" men in the paramilitary uniform had forced them to take up firearms during the first hour of the mutiny last week. "Take up arms,else none of you will survive," a BDR soldier told reporters quoting masked personnel brandishing guns and firing blank shots as saying. Most security analysts and army officers who survived the carnage earlier said it was not a rebellion but a planned killing as part of a "deep-rooted conspiracy". "Not all of them (BDR soldiers) were culprits. Many of them tried to protect us (army officers serving in BDR) risking their own lives. It was a planned killing," said army doctor Lieutenant Colonel Abdus Salam. Meanwhile,elite anti-crime Rapid Action Battalion (RAB) last night confirmed the arrests of five suspected ring leaders including the main accused of BDR mutiny case bringing them before the media at a press briefing in Dhaka. "BDR's Deputy Assistant Director 55-year-old Touhidul Alam and four other suspects named in the BDR mutiny case were arrested on the basis of the information provided by another intelligence agency," a RAB official said. The suspects,however,were not allowed to speak to the newsmen during their brief appearance before the media. The army last evening said investigators recovered more evidence like duty rosters of rebel soldiers and their mobile phone records during the bloody mutiny as three separate investigation teams including an exclusive military one were carrying out the investigations in close cooperation.