A midnight party cruise this past summer in Baltimore’s Inner Harbor ended rudely for passengers when their boat crashed into a wharf.

The cause of the crash has now become clear, the Baltimore Sun reports: The captain was asleep at the wheel.

The 119’ Spirit of Baltimore, operated by Chicago-based Entertainment Cruises, had about 400 passengers on board early on the morning of Aug. 28 when the mate left the bridge to assist with a drunken passenger, Coast Guard investigators found. Alone on the bridge, the unidentified captain fell asleep and the boat subsequently crashed into a floating pier at Henderson’s Wharf Marina, the Sun reported.

Damage to the pier at Henderson's Wharf Marina caused by the Spirit of Baltimore. USCG photo.

Damage to the pier at Henderson's Wharf Marina caused by the Spirit of Baltimore. USCG photo.

According to the report, which the Sun received through a Freedom of Information Act request, the allision did about $100,000 worth of damage to the pier, and also damaged a pair of recreational boats that were moored there, the Patty Bo and the Chapter Eleven.

Dan Leaman, general manager of Entertainment Cruises, called the captain's conduct "completely unacceptable” in a statement provided to the Sun.

"The captain was suspended and then fired within 24 hours," Leaman said. "This type of crew conduct has never occurred in the history of our company and we will continue working closely with the United States Coast Guard to ensure it never happens again."

Lawyers for three passengers have contacted Entertainment Cruises to say their clients were injured in the crash, the report said. Two passengers went to the hospital for treatment on the morning of the crash, the Sun reported at the time.

Damage to the Spirit of Baltimore was cosmetic, and it resumed cruising the day after the incident.