Leila Rohani is the fourth Iranian wanted for the blast. She is suspected of arranging to rent the Sukhumvit Soi 71 home where the three other Iranian suspects stayed and where the first explosive device exploded, apparently by accident.

The Criminal Court on Thursday issued arrest warrants for the group.

Wiboon said Rohani is now in Tehran, Iran's capital. "We could not ask Iran to extradite her to Thailand as we have no extradition treaty with the country," he said.