FORT LAUDERDALE, Fla. (AP) _ Four people jumped from a burning hot-air balloon Thursday after a fuel tank aboard exploded when the floating craft hit power lines, authorities said.

The four were hospitalized after leaping 25 feet to the ground from the gondola of the balloon, officials said. The balloon apparently had lost power and began sinking when flames died in the liquid-propane gas motor that keeps it aloft, said Fort Lauderdale police spokesman Ott Cefkin.

The balloon had taken off at about 6:30 a.m. and was trying to land at the Fort Lauderdale Executive Airport about an hour later when it became caught in heavy gusts.

''Witnesses said there appeared to have been a flameout, and the balloon started to collapse,'' said Cefkin. ''The pilot tried to start it again, but it hit power lines.''

The shock from the 138,000-volt power lines apparently caused the explosion of one of three liquid propane tanks on board, police said. When the drifting balloon hit a second set of power lines a few blocks away, the four people jumped, Cefkin said.

The most seriously injured was Kathleen Lynch, listed in serious but stable condition Thursday in Plantation General Hospital with first- and second- degree burns over 35 percent of her body, said hospital spokeswoman Anita Young.

Also injured were pilot Thomas Curley, crew member Don Brammel and passenger Vincent Provino, who works for a construction company that hired the balloon to advertise a tennis tournament. The three were in serious condition in Broward General Hospital.

The Federal Aviation Administration and the National Transportation Safety Board planned to investigate.