WASHINGTON — A crash between a nuclear-powered US submarine and a warship in the strategic Strait of Hormuz was an "avoidable" accident caused by complacent sailors and weak leadership, a Navy report said.

The crash between the USS Hartford and USS New Orleans, an amphibious vessel, on March 20 was a "catastrophic failure" of management and navigation practices on the submarine, according to the report obtained by the Navy Times through a Freedom of Information Act request.

The investigation, reported by the Navy Times on Wednesday, revealed that sailors on board the Hartford took a "lax" approach to navigating their vessel, with those assigned to keep watch often sleeping on the job.

The heavily redacted report described one navigator listening to his iPod and simultaneously taking an exam while on duty.

"This incident comes down to weak and complacent leadership, which led to inadequate planning and preparation of the crew," the report said.

Admiral John Harvey called the incident "an avoidable mishap" as he endorsed the investigation's findings.

"Correction of any one of nearly 30 tactical and watchstander errors, or adherence to standard procedure, could have prevented this collision," he added.

"In this case, the command team failed to do so, and a high price has been paid for that shortcoming."

The crash injured 15 sailors and caused the fuel tank of the New Orleans to rupture, spilling 25,000 gallons (95,000 liters) of diesel fuel.

It caused 2.3 million dollars in damage to the New Orleans, and the Hartford is still undergoing extensive repairs for costs estimated at 100 million dollars.

The Navy investigation said the New Orleans crew "bears no fault" for the crash.

The Strait of Hormuz, less than 60 miles (100 kilometers) at its widest point, separates Oman from Iran and is the gateway into the oil-rich Gulf.

An estimated 40 percent of the world's crude oil passes through the strait on the way to market.