Road Transport and Bridges Minister Obaidul Quader on Thursday said several agencies are looking into the Bhola clash to find out what really happened.
"The investigation is being carried out at the order of the prime minister. Investigators are trying to find out whether there is any conspiracy behind the incident or if communal forces are involved," the Awami League General Secretary told the media at the Secretariat.
He said anyone found guilty will be brought to book after investigation.
About the alleged involvement of Shibir activists in the assault, he said, some known faces were seen in surveillance camera footage. "Action will be taken after investigation," he said.
Asked about steps to stop spreading rumour on Facebook, he said the government was in touch with Facebook authorities. "Rumour is a global problem. Our authorities concerned are keeping in touch with Facebook authorities," he said.
Four people were killed and more than 200 others were injured on Sunday in a clash between police and demonstrating locals in Borhanuddin upazila, demanding punishment of a youth for allegedly hurting religious sentiments on Facebook.