Police searched the Delaware River off Philadelphia Saturday for an 11-year-old boy believed drowned with his uncle in a boating accident.

The body of the uncle, described as a 43-year-old man, was recovered Friday shortly after he and his nephew were swept away. Philadelphia Marine Police, New Jersey State Police and the U.S. Coast Guard were cooperating in dragging the river downstream from the point where the two disappeared, The Philadelphia Inquirer reported.

Investigators said the boy had been swimming off the 16-foot boat when he fell while trying to climb a ladder back to the boat. He was caught by the current, and his uncle jumped in to help him.

Another man who was with them said he heard the uncle calling for a rope. He said the uncle and nephew were no longer in sight when he tried to throw the rope.

Philadelphia Police Officer Anthony Kowalski said no one in the party was wearing a life jacket or other flotation device.