A charter plane carrying 143 people and traveling from Cuba to north Florida ended up in a river at the end of a runway Friday night, though no critical injuries or deaths were reported, officials said.

A Boeing 737 arriving at Naval Air Station Jacksonville from Naval Station Guantanamo Bay, Cuba, with 136 passengers and seven aircrew slid off the runway into the St. Johns River, a NAS Jacksonville news release said.

The Jacksonville Sheriff's Office posted on Twitter that a marine unit responded to assist. The plane was in shallow water and not submerged. Everyone on the plane was alive and accounted for, the agency posted, with 21 adults transported to local hospitals in good condition.

A photo posted by deputies shows a Miami Air International logo on the plane. The company didn't immediately respond to messages from The Associated Press.

Capt. Michael Connor, the commanding officer of NAS Jacksonville, said during a news conference that passengers were a mix of civilian and military personnel. Some were staying in the area, while others were set to fly on to other parts of the country.

While the crash certainly wasn't ideal, Connor acknowledged that it could have been much worse.

"I think it is a miracle," Connor said. "We could be talking about a different story this evening."

It wasn't known how long it would take to remove the plane from the river, but Connor said the landing gear appeared to be resting on the river bed, making it unlikely for the aircraft to float away. He said crews began working to contain any jet fuel leaks almost immediately after securing the passengers' safety.

Liz Torres told the Florida Times-Union that she heard what sounded like a gunshot Friday night from her home in Orange Park, about 5 miles (8 kilometers) south of NAS Jacksonville. She then drove down to a Target parking lot where police and firefighters were staging to find out more.

"I've never seen anything like this," she said.

The Jacksonville Fire and Rescue Department posted on Twitter that approximately 90 personnel responded to the scene, adding that the department's special operations team had trained with marine units for a similar incident earlier Friday.

Navy security and emergency response personnel were on the scene and monitoring the situation, the Navy release said. Family members who were expecting the arrival of passengers were instructed to stand by.

Officials did not immediately say what caused the plane to leave the runway. Boeing said in a tweet Friday night that it was investigating: "We are aware of an incident in Jacksonville, Fla., and are gathering information."

The Federal Aviation Administration was referring media inquiries to NAS Jacksonville.

Connor said National Transportation Safety Board investigators were already on their way.