Authorities are investigating the cause of an explosion aboard a cargo ship that was leaving the Port of Baltimore when it issued a mayday call.

An explosion aboard a cargo vessel in Patapsco River caused no injuries late Monday and is under investigation, Baltimore and federal officials said.

An explosion erupted on a cargo ship hauling coal in Baltimore’s harbor near the Key Bridge collapse site Monday evening, according to news sources. The explosion, which has been fully contained, started at 6:28 p.m., Baltimore City fire officials told WBALTV11. The ship was full of coal and had just left the CSX Coal Dock.