The main channel used by cargo ships to enter and exit the Port of Baltimore was still shut down Tuesday morning as the Coast Guard probed the cause of a Monday evening explosion on board a coal carrier.

The Port of Baltimore’s main shipping channel was closed for several hours Tuesday while crews worked to locate a hatch from the ship that detached during the explosion and fell into the water, officials said. They announced late Tuesday afternoon that the channel had reopened.

An explosion rocked a cargo ship carrying coal in Baltimore, causing a fire and sending a stream of smoke into the sky but leaving no injuries, authorities said Monday evening.