Law enforcers said the trio were top JMB leaders.
Of them, Salauddin Salehin alias Sunny, 38, and Raqibul Hasan alias Hafez Mahmud, 35, were death row convicts and Jahidul Islam alias Bomaru Mizan, 35, was sentenced to life in jail.
The prison van was transporting them to a court hearing in Mymensingh from Kashimpur Central Jail in Gazipur when the attack took place, sending ripples across Bangladesh.
One of them, Mahmud, got arrested several hours later in Tangail.
Meanwhile, borders are on red alert to stop the fleeing militants from crossing over to India and Myanmar while a massive manhunt is on-going . A bounty of Tk 200,000 has also been declared for information on each of the fugitives.
The attack on the prison van left Constable Atiqul Islam, 30, killed and two other policemen injured.
Police, however, have managed to arrest three people for their involvement in the Hollywood-style hold-up.
State Minister for Home Asaduzzaman Khan Kamal said efforts were on to arrest the remaining two. “We hope to catch them soon.”
The home ministry and police have formed two separate investigation committees on the matter. The teams have been asked to report in three days.
In the meantime, two members of Gazipur police have been punished for negligence of duty.
Securities at all the prisons in the country have been heightened after the attack at Trishal. Watch on the militants behind bars have also been heightened.
In another event, BNP Standing Committee member Rafiqul Islam Miah has expressed concern over the incident and demanded arrest of the fugitives within 12 hours.