The government minister co-ordinating the inquiry into a mutiny by Bangladesh border guards has said he believes Islamic militants were involved.
More than 74 people were killed in the violence, mostly senior army officers.
The government says investigators have now uncovered a link between the mutineers and a militant group responsible for a series of bombings.
Commerce Minister Farukh Khan said some of those arrested had links to the Jumatul Mujahedeen Bangladesh (JMB).
Mr Khan is co-ordinating the separate inquiries being carried out by the government, the army and the police.
The BBC's Mark Dummett in Dhaka say that the JMB in its most daring attack detonated 400 bombs on the same day in 2005.
In an interview with the AFP news agency, the minister said that the link to the JMB had been made during the interrogation of the 40 soldiers of the Bangladesh Rifles (BDR) border force who had now been arrested.
At least 57 army officers were killed in the mutiny
"We have found in the process of examining their files that some of them have links to the JMB," he said.
"The suspects were BDR troops. We are asking why these kinds of people were recruited to the BDR.
"There are a number of figures we have not been able to finalise yet, including the exact death toll, how many people were involved, and how many ran away," Mr Khan said, adding that many weapons were missing from the BDR base.
In total the police have issued more than 1,000 arrest warrants for men allegedly involved in the revolt and the deaths which followed.
On Wednesday, detectives from Britain's Scotland Yard arrived in Bangladesh to help investigate the mutiny.
The four-member police team was invited by Prime Minister Sheikh Hasina and will work with local and US detectives.
Sheikh Hasina has said last month's mutiny was part of a conspiracy to bring down her new government.
On Wednesday the authorities said they had identified some of those who carried out the killings from among mutineers being held.
Law minister Shafique Ahmed has said there may be special tribunals or courts martial for the mutineers.
Charges already drawn up include conspiracy to kill officers and civilians, using weapons and explosives, creating panic, looting and trying to hide bodies.