The 11 injuries that came after a possible boat explosion in Miami may be tied to the boat's hatches that were allegedly not open when the ignition was started, an eyewitness told local media outlet CBS12.

Miami-Dade Fire and Rescue Battalion Chief Juan Arias said first responders were dispatched around 12:48 p.m. on May 9, USA TODAY reported, after reports of an explosion in the waters off Miami's Haulover Sandbar.

Crews arrived and located multiple victims. Eleven people were treated at the scene before being transported to area hospitals. Arias told USA TODAY some of the victims sustained burn injuries, though he did not comment on the full extent of their conditions.

Officials told USA TODAY May 10 the cause of the possible explosion is is under investigation.

Ongoing investigation: Multiple people injured in possible boat explosion near Miami sandbar

Speaking to CBS News Miami, Patrick Lee, a boat charter captain who witnessed the incident, described seeing "three people fly out of the boat" after the explosion. Lee speculated that gasoline fumes ignited after the boat was started, causing the explosion.

"People got on board, and he turned the key and didn’t open the hatches, didn’t turn on the blowers, and he blew people out of the boat," Lee told the outlet.

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Witnesses told CBS12 that emergency crews responded to the scene "within minutes." They described passengers suffering burns being carried away on stretchers. "I just saw a lot of them were burns all over them," Lee said. "It is quick. But it’s high octane gasoline."

More than 25 units from four organizations responded to the scene, including the local fire department, an Ocean Rescue team, the Florida Fish and Wildlife Conservation Commission and U.S. Coast Guard, according to CBS12.

"This time of year we have a lot of boats on the water, so it’s always good to make sure you have a radio with you, life vests, fire extinguishers," Arias told CBS12, "and also an experienced boater with you on the boat."

This article originally appeared on USA TODAY: Miami boat explosion that injured 11 remains under investigation