Washington (CNN) -- A ferry accident two years ago in Staten Island, New York, was caused by a technical malfunction, according to a federal investigation. Fifty people were injured, three seriously.
The National Transportation Safety Board's final report released Tuesday explains why the 310-foot-long Andrew Barberi slammed into the St. George terminal on May 8, 2010.
The NTSB found the crash was caused by a malfunction of a solenoid, a part of the propulsion control unit in the ship's bridge, which "rendered one of the vessel's two propellers unresponsive to propulsion commands ..."
"The pilothouse crewmembers were unaware of the loss of propulsion control until seconds before the accident," the board determined, and the crew was unable to avoid the crash.
"As soon as we got to the port, it just slammed right into the dock and pushed everybody back. It was chaos, pandemonium. It was something like I've never been through in my life," passenger Alex Gonzalez told CNN affiliate New York 1 at the time.
The NTSB says the crew might have reacted in time to prevent the accident if there had been an audio and visual alarm to warn the crew the propeller was not responding as commanded.
These types of alarms were not required for vessels such as the Barberi.
The board recommended the Coast Guard require all new passenger vessels to have such an alarm and older vessels be retrofitted where technically feasible.
The Andrew Barberi was the same ferry involved in another accident on October 15, 2003, when 11 passengers died and 70 were injured after the boat hit a maintenance pier in Manhattan.
The NTSB ruled that crash was caused by the "assistant captain's unexplained incapacitation and the failure of the New York City Department of Transportation to implement and oversee safe, effective operating procedures for its ferries."
Tuesday, the NTSB praised improvements since the 2003 accident saying in the report the "safety management system provided specific emergency procedures, which the crew and shore side personnel performed in a timely and effective manner, and this benefited the passengers."
"They had a lot of stuff in place that really made a difference," noted Mark Rosekind, NTSB member.
The Barberi was repaired after each of the accidents and rejoined the ferry fleet.
Each workday, five ferries carry 65,000 people on the 5.2 mile route between Staten Island and Manhattan, according to the New York City Department of Transportation.