John B. (Jack) Kelly Jr., 57, the president of the U.S. Olympic Committee and former Olympic rowing medalist who was a brother of the late Princess Grace of Monaco, collapsed and died March 2 while jogging in Philadelphia.

Police said Mr. Kelly died after an apparent heart attack. The Philadelphia medical examiner's office expects to have the result of an autopsy on Mr. Kelly sometime today, a spokesman said.

Police said that Mr. Kelly was found clad in running clothes near a downtown intersection about 9:30 a.m.

Mr. Kelly, who won a bronze medal in the single sculls in the 1956 Olympics at Melbourne, Australia, was elected president of the USOC last month -- a position he said in an interview he had "looked forward to for a long time."

"I got a lot out of sports, and I'd like to contribute something back," said Kelly, a lifelong rower, swimmer and amateur sports enthusiast.

Mr. Kelly also competed in Olympic Games in 1948, 1952 and 1960. In 1947, he won the James E. Sullivan Award as the nation's outstanding amateur athlete.

A Democrat, he had served on the Philadelphia City Council from 1968 to 1970.

Mr. Kelly was a graduate of the University of Pennsylvania and was president of John B. Kelly Inc., a Philadelphia bricklaying firm that his father, John B. Kelly Sr., started in the early 1920s. His father had won gold medals in two Olympics for sculling.

Mr. Kelly had served as president of the International Swimming Hall of Fame in Fort Lauderdale, Fla., and was chairman of the Philadelphia Athletic Committee.

Survivors include his wife, six children, his mother, and two sisters.