Sri Lankan police have detained 16 more people for questioning overnight, taking the number of arrested since Sunday to at least 76.
An Egyptian, Syrian and several Pakistanis were among those detained for questioning as the police probed deeper into the Easter Sunday bombings.
In a statement, police said one of those detained on Wednesday night was linked to a "terrorist organisation" but gave no other details.
Another person was taken into custody for "spreading and preaching of terrorism" on Facebook.
On Thursday, an explosion occurred in a town east of Colombo, but there were no casualties.
The government has acknowledged its failure to prevent the attacks despite receiving intelligence tip-offs.

Iran studying deal to halt war as stalemate persists
WHO says suspected Ebola cases drop to 116 after hundreds ruled out
Israel strikes south Lebanon after holding off Beirut attack
At least 22 killed in heavy Russian attack on Ukrainian cities
Two killed in Kenya protest against US Ebola quarantine facility as Ruto defends plan
