Swedish police said they had arrested a second suspect linked to the deadly truck attack in Stockholm this month.
The unnamed person was detained on Sunday on the order of prosecutors, the force said, without going into further details on the suspected offence.
Four people were killed and 15 injured when a truck ploughed into a crowd on a shopping street and crashed into a department store in the centre of the capital on April 7.
The suspected driver, an Uzbek asylum seeker named by police as Rakhmat Akilov, is already in custody.
Police said the second arrest had followed the examination of unspecified material gathered after the attack.