More than 70 suspects have been arrested across the country since Sunday, Sri Lankan police spokesman, Ruwan Gunasekera, told CNN.
He said the suspects have been arrested on suspicion of terrorism, aiding and abetting and conspiracy to commit terrorism.
He also says the four most serious cases are in the custody of the Terrorism Investigation Department (TID). A further 33 suspects are in custody of the Criminal Investigation Department (CID). All remaining suspects are being held by local police.
The majority of the suspects were arrested in Colombo, four of which are women. All of the suspects are from Sri Lanka and most are family members and friends of the suicide bombers.