Device explodes in South Boston

An explosive device has gone off in South Boston and police say it was a deliberate act.

The device with a propane tank blew up near a police cruiser.

Police Commissioner William Evans said the explosion in South Boston during the morning rush hour set the cruiser on fire but no one was hurt.

Evans said the federal Joint Terrorism Task Force has been called in to help with the investigation. He called the incident "troubling."

Evans said the propane tank was positioned between the decking for a bridge and the passenger side of the parked cruiser and police are studying surveillance videos from the area.

"We are going to find out who is responsible," Evans said.

The Boston division of the FBI said it is assisting police in the investigation.

"We are postured to provide any resources that are needed and we are working closely with the Boston Police Department in identifying who is responsible," the FBI said in a statement.