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.
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