A piece of wreckage was found Monday on a beach several miles from the area where a boat was reported to have sunk with nine people on board, but no other trace of any vessel had turned up, the Coast Guard said.

No one had reported any boaters missing, officials added.

The Coast Guard said it received a call late Sunday from someone who said all five adults and four children aboard a 33-foot powerboat had put on life jackets. The man said his wife had broken her leg and was bleeding, and said they were 3 miles off Boynton Beach Inlet on Florida's Atlantic Coast.

The man maintained contact with a handheld radio after the boat went down, but the signal went dead after about an hour, officials said.

A beachcomber found a piece of boat hull Monday, but officials didn't know if it came from the vessel mentioned in the distress call, Coast Guard Lt. Cmdr. Chris O'Neil said. It appeared to be from the edge of a white boat with fishing pole slots.

"There have been no other debris sightings, something that would indicate the sinking of a vessel, the things we would normally find," O'Neil said. "Given the rapid response we had to this incident, I find it unusual that we haven't found any signs of wreckage."

O'Neil said it was also unusual that authorities had not received any calls from relatives of the missing boaters.

"In general, when folks are overdue or missing, someone misses them, an employer, friends, relatives, a marina operator," he said.

The Coast Guard and local agencies sent aircraft and boats to search a 50-mile stretch from St. Lucie County to Boynton Beach.

Waves were 3 to 4 feet Sunday night in the area where the boat reportedly sank, about 50 miles north of Miami. Conditions were much the same Monday but were expected to deteriorate as Tropical Storm Alberto approached Florida from the west.