Police ruled out yesterday the possibility that an explosion at the Alpheios dam, western Greece, may have been a deliberate act of sabotage. The explosion occurred early yesterday next to a room housing the control mechanisms for the dam’s barriers. Authorities said that the operation of the barriers was faulty but would not confirm whether this was the result of the explosion. It is more likely that an explosive device was used to break into the facility for the purpose of theft, a police source said. Authorities said that a night-time security guard had been hired last week to patrol the area but was expected to start his first shift only last night. Repair work has since been completed and the dam’s barriers are again operating properly.