Two Hungarian exchange students killed in a tourist boat accident in Philadelphia were remembered at a special service Saturday, according to dpa. Fellow exchange students, boat passengers, Philadelphia Mayor Michael Nutter and Hungarian ambassador Bela Szombati attended the service, the Philadelphia Inquirer reported online. Nutter apologized on behalf of city for the tragedy. Szabolcs Prem, 20, and Dora Schwendtner, 16, were killed when a barge collided with a tourist boat Wednesday on the Delaware River in the eastern US city of Philadelphia. The amphibious craft known as a duck boat, which took tourists to historic sites on land and water, had 35 people on board. Nine people were hospitalized with minor injuries and the two students went missing after the boat capsized. The boat had experience mechanical difficulties and there had been a fire on board before a barge plowed into the craft, police said in a televised press conference. Family members of the victims were unable to attend the service, which drew friends and teachers from the three-week exchange trip.