Sri Lanka’s airport in the capital Colombo was shut briefly over a bomb scare on Thursday and more people were swept up in the search for Easter Sunday bombings perpetrators.
Police arrested many people and seized 21 locally made grenades and six swords during a raid in Colombo.
Foreigners were swept up for questioning as Sri Lankans and international authorities probed deeper into the bombings.
Egyptian and Pakistanis were among the detained.
There was no immediate suggestion they had direct links to the attacks.
At least 359 people were killed and about 500 wounded in bomb attacks in Sri Lanka, the deadliest operation claimed by Islamic State.
The street outside the building near the World Trade Center in the capital and the entry road to Colombo’s main airport were blocked after a suspicious vehicle was identified at a nearby carpark.
The authorities said, their investigation has led to well-educated, home-grown Islamist suicide bombers, including a woman, and they believe they have links to domestic and international Islamist groups such as National Thawheed Jama’ut and Jammiyathul Millathu Ibrahim.
Islamic State offered no firm information to back up its claim of responsibility.