Lebanon’s security forces arrested a Lebanese man on Wednesday in connection with twin suicide bomb attacks that killed 44 people in Beirut last week, a security source said.

The authorities had arrested five Syrians and a Palestinian linked with the attacks, which took place on Thursday in a crowded residential and commercial area of the capital. They were claimed by ISIS.

Wednesday’s arrest took place in Beirut, the source said, without elaborating.

Security forces say their investigations into the bombings have led to arrests of other people without direct links to the attacks and the seizure of large amounts of explosives.

The explosions targeted innocent civilians in the latest spillover of violence from the Syrian civil war across the border.