Federal investigators on Saturday began searching for what caused a Boeing jetliner with 143 people on board to slide off a runway into a shallow river while landing at a Jacksonville, Florida military base during a thunderstorm, injuring 21 people.

The Boeing 737-800 chartered by the U.S. military was arriving from Naval Station Guantanamo Bay in Cuba with 136 passengers and seven crew members when it slid into the St. Johns river at the end of the runway at Naval Air Station Jacksonville on Friday night, authorities said.

No one was badly hurt and the 21 people taken to a hospital were listed in good condition, the local sheriff's office said.