( CNN ) -- The U.S. Coast Guard on Saturday released recordings of radio communications after this month 's collision between a tour boat and a barge in Philadelphia , Pennsylvania . Thirty-seven people were on board the smaller duck boat in the Delaware River on July 7 when the accident occurred . Two people , both from Hungary , were killed . `` Hey ferry , ferry , ferry ! Whoa , whoa , whoa , whoa , whoa ! '' an unidentified voice yelled early in the incident , apparently witnessing the collision . A tug boat then called in to a Coast Guard radio center . `` This is Freedom . We got people in the water on Penn 's Landing . It looks like they got run over by a barge . One of the duck boats . I am going in to pick 'em up . '' `` Roger , captain . How many persons are in the water ? Over . '' `` No idea . I do n't have time to talk to you right now . I am going to get the people . '' The Coast Guard radio operator then advised other vessels to assist in the search for the 37 passengers . Duck boat crew members told investigators that they made radio calls to the tug boat Caribbean Sea that were not answered prior to the collision , the National Transportation Safety Board said earlier this month . The Caribbean Sea was pushing the barge that collided with the tour boat , causing it to sink in 55 feet of water , the report said . The skipper of the Caribbean Sea can be heard on the recordings , responding to a Coast Guard call . `` We are right here next to the ship Freedom . We are the ones that , I guess , capsized the duck boat . We 're on scene just making sure that no one got injured or if we can help in anyway . We do have a barge alongside , so there 's not too much we can do . '' The Coast Guard radio person then asked him to throw any needed life jackets into the water . One of five crew members of the Caribbean Sea invoked his Fifth Amendment right against self-incrimination and declined to meet with investigators , the safety board said earlier this month . According to CNN affiliate WPVI , these recordings are just some of the many elements federal investigators are reviewing as they probe the circumstances surrounding the collision . They also continue to examine the structural damage of both vessels . The tour boat , the DUKW 34 , carried 35 passengers and two crew members when it experienced mechanical problems about five to 10 minutes before the crash , the NTSB report said . That problem led the ship 's master to anchor the tour boat . Meanwhile , the Caribbean Sea approached with the barge . Around 2:36 p.m. , the bow of the barge hit the small tour boat , causing it to sink , investigators said . People who operated several vessels in the area have told federal investigators that they heard the tour boat 's radio calls . The National Traffic Safety Board said it 's looking into those accounts .
Coast Guard releases audio communications made after barge - tour boat collision . The captain of a tug boat says his barge was responsible for hitting the duck boat . Investigators are still looking into the collision 's cause . Two people were killed in the collision .