Lakshman Kiriella, who is also minister of public enterprise, said more than 100 people were likely to be arrested, without giving further details.
Initial investigations confirmed there were 9 suicide bombers and 8 of them were identified, according to the Sri Lanka police.
One of the nine bombers that detonated explosives in Sri Lanka on Easter Sunday was a woman, deputy defence minister Ruwan Wijewardene told reporters on Wednesday.
The blasts at hotels and churches have so far killed at least 359 people, the deadliest such event in south Asia's history.