Senior Judicial Magistrate Md Shariful Islam of Sirajganj Chief Judicial Magistrate Court passed the order after Investigation Officer Md Monir Hossain produced them before the court on Saturday.
Earlier on February 13, the court put them on a five-day remand each.
Shimul, a correspondent of the daily “Samakal,” was fatally shot by Mayor Miru when he was covering a factional clash of the ruling Awami League on February 2.
He died the next day.
Shimul’s wife sued 18 people, including the mayor, for her husband’s death.
The mayor was arrested in Dhaka on February 5.