SAN DIEGO -- A charity that stages free sailing trips for people with special needs said Tuesday a gust of wind caused an accident that killed two passengers and dumped eight others into the cold water of San Diego Bay.

The account by the Heart of Sailing Foundation came as authorities investigated the deaths and the manufacturer of the boat raised questions about the number of people aboard during the accident.

The 26-foot MacGregor sailboat capsized Sunday, killing the grandfather and uncle of an 11-year-old autistic boy who was one of nine guests on the excursion along with the driver of the vessel, the charity said. One other disabled person was onboard.

John Shean, an attorney and president of the board for the Bloomington, Ind.-based foundation, said the boat capsized after a gust of wind caught the jib, the only sail raised at the time.

Charity's founder George Saidah was piloting the boat and frequently took nine passengers on trips on the craft, said Shean, who received an account of the accident from Saidah by phone.

"Obviously a sailor will tell you that when a boat capsizes the pressure of the wind on the sail basically exceeds the center of gravity, and it capsizes," Shean said. "It was windy that day, there was a gust and he released the jib to let it fly out more so that it doesn't catch the wind."

However, Roger MacGregor, the maker of the boat built in 1988, challenged the wisdom of putting 10 people onboard and questioned whether water ballast, which helps the ship automatically right itself, was properly filled.

MacGregor, of Costa Mesa-based MacGregor Yacht Corp., said authorities had called him several times during their investigation with questions about the boat.

He told The Associated Press the model had no specifications on weight limit or number of passengers but could become dangerously unstable with 10 people onboard.

The number of people who could be safely accommodated also would also depend on wind and wave conditions and the experience level of the passengers, he said. If passengers stayed still at the center of the boat, more could safely ride, he said.

"It's a relatively small boat. The weight of the people outweighs the ballast on the boat if you give an average of 145 pounds or so per person," MacGregor said. "It was grossly overloaded in my opinion. There's nowhere for them to sit."

Shean insisted the ballast was full and contended the boat was not overloaded.

Saidah "had sailed without incident many times with nine passengers and himself, and if the manufacturer believes that it is grossly overloaded to have 10 people on the boat than they should have notified through some warning or manual or notice," Shean said.

San Diego Harbor Police Sgt. Brian Jensen didn't immediately return calls Tuesday. Authorities have been tight-lipped about the investigation.

Peter Knudson, a spokesman for the National Transportation Safety Board, said his agency was aware of the accident but was not currently involved in the investigation.

Some of the people aboard were not wearing life jackets, but it had not been determined how many, said Harbor Police Chief John Bolduc, whose agency is leading the investigation.

Shean said California law only requires children to wear life preservers.

Bolduc previously said investigators were looking into whether the boat was overloaded. The weight on board -- not the number of passengers -- would determine if that was a factor, he said.

Bolduc declined further comment Tuesday through spokesman Ron Powell.

MacGregor said investigators have also questioned him about the function of the ballast system on the boat and appear to be focusing on whether it was full.

The sailboat has a large, 1,200-pound water tank that runs along the centerline of the hull, he said, explaining when the tank is full, the boat should spring back up immediately if it leans too far into the water and begins to capsize.

"If the tanks were empty it conceivably could roll over," MacGregor said. "We're pretty clear: don't operate the boat with the tanks not full."

The group's website says Heart of Sailing was founded in 2004 by Saidah, a software entrepreneur and sailor who was motivated by his experience with a loved one with a cognitive disorder.

The website boasts "a 100 percent satisfaction and safety record."

Chao Chen, 73, and his son, Jun Chen, 48, of San Diego, died in the accident. They were among seven members of one family aboard, said San Diego Fire-Rescue spokesman Maurice Luque.

Shean identified the dead men as the relatives of the autistic boy. His 9-year-old sister, who was not special needs, also was on board, Shean said.

He did not know the identities of the other passengers or their relationship to the two deceased men.

That account conflicts with initial information from authorities, who said the two special needs passengers were young adults. The discrepancy could not be immediately resolved.

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On the Net:

Heart of Sailing Foundation: http://www.heartofsailing.org/default.asp

MacGregor Yacht Corp.: http://www.macgregor26.com/

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AP writer Gillian Flaccus reported from Tustin, Calif.