PHILADELPHIA — The mate piloting a tug boat in last summer's deadly collision of a tourist boat and a barge was consumed by a family emergency and on his cell phone at the time, a new government report on the crash revealed Monday.

The mate told a tugboat company lawyer he had learned that day of a life-threatening medical emergency involving his young son, the National Transportation Safety Board report said. The mate, who was not identified, made or received 21 calls on his personal cell phone from the time he took the wheel at noon until the 2:37 p.m. crash.

The barge struck a disabled amphibious "duck boat" on July 7, killing two Hungarian students and plunging 35 other people into the Delaware River. The NTSB report does not analyze what caused the crash.

The 4,400-page report released Monday also said the mate did not assign a lookout on the high-sitting barge as it was being pushed from behind by the small tug.

A federal criminal investigation is also under way. At his lawyer's advice, the mate has declined to cooperate with NTSB investigators, citing his Fifth Amendment right to avoid self-incrimination.

His defense lawyer, Frank DeSimone, said Monday that he had not yet read the new report and declined to comment.

The parents of the Hungarian students killed, 20-year-old Szabolcs Prem and 16-year-old Dora Schwendtner, have a wrongful death lawsuit pending against the city, which owned the barge, and operators of both the tug and the amphibious duck boat.

Ride the Ducks, the tour boat company, has not resumed its land-and-water tours in Philadelphia.

The tour boat's radio calls to the approaching tug went unheeded in the moments before the collision, the NTSB found. The mate, in brief statements the day of the crash, told investigators he did not hear, see or feel anything before seeing people in the water, the NTSB said.

Drug and alcohol tests on the crews of both vessels were negative, the NTSB has said.