TEHRAN, Iran — Iran's official IRNA news agency reports that an elevator at a construction site plummeted multiple floors, killing six construction workers in the capital Tehran.

Jalal Maleki, spokesman for the Tehran Fire Department, tells IRNA the incident took place Tuesday night in the Chitgar district. Unofficial reports said the elevator plunged more than 20 stories.

The semi-official ISNA news agency reported that three Iranians and three Afghan workers were killed.

The cause of the incident is under investigation.

Safety measures are often poorly enforced in Iran.