Twenty-six suspects have been arrested in connection with the killing of 207 people.
They are being detained and interrogated by the Criminal Investigation Department officials, the police spokesman said.
Two suspects have been arrested in the Dambulla area for allegedly smuggling explosives.
They are residents of Kaththankudi and Mawanella areas.
13 suspects were arrested in connection with the Dematagoda hospital explosion in the Colombo Crimes Division.
The driver of the van was arrested with the van.