Witnesses reported an explosion in a van near a Colombo church as Sri Lankan bomb squad officials were trying to diffuse it on Monday. Just moments before, a spokesman said the Sri Lankan police found 87 bomb detonators at the main bus station in the capital city just one day after suicide bombers attacked churches and hotels killing 290 people and wounding about 500.
Security forces are carrying out searches across the island to find those behind the bombs. No group has claimed responsibility.
A Sri Lankan government official says a local militant group named National Thowfeek Jamaath is responsible for the Easter Sunday suicide bombings.
Health Minister Rajitha Senaratne said at a news conference Monday that all seven bombers linked to the near-simultaneous attacks on three churches and three luxury hotels in and around Colombo were Sri Lankan citizens.
Officials say the causes of three later bombings on Sunday are still being investigated.
He said that while the group is domestic, foreign links are suspected.
A total of nine bombings Sunday killed at least 290 people including at least 27 foreigners. About 500 others were wounded in the blasts.