The amphibious tour boat's radio calls to the approaching tug went unheeded in the moments before the July 7 collision near Penn's Landing on the Philadelphia waterfront, the National Transportation Safety Board found in its preliminary report, according to marine radio traffic recordings.
Drug and alcohol tests on the crews of both vessels were negative, the report said. The mate piloting the tugboat declined to answer investigators' questions, citing his Fifth Amendment right against self-incrimination.
All 35 passengers and two crew members aboard the boat operated by Ride the Ducks tours were tossed into the water when the 250-foot barge plowed over the 33-foot duck boat, sinking it. Most were rescued by firefighters, a passing ferry boat and passers-by on shore. The two Hungarians drowned.
The two killed - Dora Schwendtner, 16, and Szabolcs Prem, 20 - were touring the city as part of a church-sponsored exchange program. Their parents have since sued the city and the operators of both vessels.
Their lawyer, Robert Mongeluzzi, said the newly disclosed tapes referenced in the report confirm that "the tugboat blindly pushing the barge up river was totally deaf to repeated distress calls from the duck boat and others."
Darrell Wilson, a spokesman for the tug operator, K-Sea Transportation Partners of East Brunswick, N.J., said in a statement that the company didn't want to comment until the investigation was complete and findings and recommendations have been released.
The amphibious boats are a popular way for tourists to sightsee from both land and water.
Mongeluzzi, however, said the NTSB report does not address his concern about the safety of their canopies, which he believes can trap people underwater if the boats submerge.
He wants duck boat operations in other cities suspended as they have been in Philadelphia since the crash.
Ride the Ducks said the report shows its staff tried to avert the crash by calling the tug.
"Today's preliminary report unequivocally shows our captain's repeated distress calls on the established broadcast channel went unanswered although they were heard and retransmitted by other vessels in the area," Ride the Ducks President Chris Herschend said in a statement. "The question remains why did these calls go unanswered and why won't the first mate cooperate in the investigation."
The NTSB's two-page preliminary reports gives a glimpse of the government's initial findings, but does not offer analysis or any conclusions on the cause of the crash. The agency will later issue a more extensive report.
The mate piloting the tug has not been identified. His lawyer, Frank DeSimone, said he advised his client not to talk to federal investigators. DeSimone declined comment on the NTSB report.