“We saw three people fly out of the boat,” eyewitness and local boat charter Patrick Lee told the BBC’s US partner CBS News.
“I just saw a lot of them with burns all over them, and I said that it’s a hot fire,” Lee added. “It is quick, but it’s high octane gasoline, and so a lot of them got burnt and it was an explosion.”
Videos from the scene appear to show a helicopter landing close to the Miami marina with emergency teams carrying at least one injured person on a stretcher.
Fire and rescue teams were joined by the US coast guard and Florida Fish and Wildlife Conservation in responding to the incident.
Haulover Sandbar is billed as a popular tourist marina in Miami, owing to its clear and shallow water.