A Ride the Ducks boat stalled on the Delaware River on Sunday afternoon, just a day before the start of a federal trial stemming from the 2010 accident in which a barge hit a stranded duck vessel, killing two passengers.

On Sunday, the 26 passengers and two crew members were towed safely to shore within four minutes, the boat company said.

After the 2010 accident, Ride the Ducks and the Coast Guard created a new safety plan that required a standby rescue boat to be available at all times during duck tours.

That plan also has the ducks follow a much shorter route that company officials have said keeps their vessels far away from larger boats.

A mechanical problem caused the boat to stop on the water about 1:30 p.m. Sunday. A company spokesman said no cause had been determined.

"At no time were passengers in harm's way," said Greg Blumenthal, Ride the Ducks' Philadelphia general manager.

"Like any other mechanical vehicle, vessels may sometimes stall," he said. "The important point was that our safety procedures worked just as they had been planned and practiced."

Duck Boat 30 will remain off the water until the source of the problem has been identified, a Coast Guard representative said.

The rescue boat used a hip tow, securing the duck boat alongside it, to haul it back to shore.

On July 7, 2010, duck-boat captain Gary Fox saw smoke on the boat and shut it down while awaiting help. As the duck sat idled, the barge ran into it, sending the passengers overboard.

A National Transportation Safety Board investigation determined that Matthew Devlin, the first mate on the tug pushing the barge when it crashed into the duck boat had been distracted by a medical emergency involving his child and was on his cellphone and laptop when he should have been keeping watch on the Delaware.

In November, Devlin was sentenced to a year in prison after pleading guilty to involuntary manslaughter.

On Monday, lawyers for the families of the two victims will begin arguments in a federal case that will determine whether an 1851 law limiting liability in maritime accidents applies to this case. The Schwendtner and Prem families are in Philadelphia for the trial.

K-Sea Transportation Partners, which owned and operated the tugboat, and Ride the Ducks argue that federal law limits their liability in the accident to the value of the boats, about $1.8 million.

Robert Mongeluzzi, a lawyer for the families, will argue that there should be no such limit. On Sunday, he said he was not surprised a duck boat had stalled again.

"They are probably the only fleet in the world where the vessels are so unreliable that they need a second vessel there in the case of emergency," Mongeluzzi said.

Officials for Ride the Ducks have maintained that the boats are safe and that Devlin's negligence was the primary cause of the accident.