Boeing 737 Plane With 143 On Board Skids Into St. Johns River In Jacksonville

Enlarge this image toggle caption Jacksonville Sheriff's Office, via Twitter Jacksonville Sheriff's Office, via Twitter

Updated Saturday at 3:20 a.m. ET.

A Boeing 737 aircraft arriving at the naval air station in Jacksonville, Fla., from Guantanamo Bay, Cuba, skidded into the St. Johns River on Friday night.

All 136 passengers and seven flight crew members on board are alive and accounted for, officials at Naval Air Station Jacksonville said in a statement. Twenty-one adults were transported to local hospitals with minor injuries reported.

"Non-critical status is what we had of the 21 individuals transported [to local hospitals]," Jacksonville Fire and Rescue Department spokesman Tom Francis said.

Officials did not immediately say what caused the plane to leave the runway.

During a news conference, Capt. Michael P. Connor, the commanding officer at Naval Air Station Jacksonville, said "the cause of the mishap has yet to be determined." He said the aircraft's passengers were a mix of civilians and military personnel.

"I think it is a miracle," Connor told reporters. "We could be talking about a different story."

After securing the passengers' safety, Connor said crews began working to contain any jet fuel leaks, according to the Associated Press.

The jet, which went off the runway at 9:40 p.m. ET, was in "shallow water" and "not submerged," the Jacksonville Sheriff's Office said on Twitter.

Navy security and emergency response personnel were on the scene, and an investigation into the accident is currently underway, according to the Navy's statement.

Connor said the National Transportation Safety Board is heading to Jacksonville to try to determine what went wrong.

Boeing also said it was investigating the incident.

"We are aware of an incident in Jacksonville, Fla. and are gathering information," the company said in a tweet.

Jacksonville Mayor Lenny Curry posted multiple updates on Twitter throughout the night. He said the White House called to help as the situation unfolded.

This is a developing story. Details may change as more information becomes available.