BILLINGS, Mont. (AP) — A crew member remained hospitalized Tuesday after violent turbulence triggered “pandemonium” aboard a United Airlines flight into Billings and sent passengers and crew flying through the cabin, according to company representatives and passengers.

Ejay Old Bull said drinks had just been served and passengers were moving around the cabin on the flight from Denver when the plane started to lurch violently with no prior warning, approximately 55 minutes into the hour-and-a-half flight.

“It was a solid 20 seconds of pandemonium,” said Old Bull, a 26-year-old graduate student who was returning to school at Billings’ Rocky Mountain College. “What really hurt people and what really got everyone panicked was when the plane tipped to the right and dropped for about four or five seconds. That’s when people started praying.”

Old Bull said he watched his unrestrained seatmate crash headfirst into the overhead luggage bin and briefly lose consciousness. Meanwhile, a crew member was bouncing around in the galley just behind his seat, Old Bull said.

Federal safety officials said they were looking into the incident that left three crew members and two passengers injured.

No details were available on the condition of the female crew member who remained hospitalized. United spokeswoman Christen David said an airline supervisor was by her side at the hospital.

The Boeing 737-300 involved has been taken out of service while the airline reviews what happened, David said.

“Our flight safety investigators are working closely with the NTSB to analyze the flight data,” she said in an emailed response to questions.

Flight 1676 encountered the unusually rough turbulence Monday afternoon while flying over Wyoming at an altitude of 34,000 feet, authorities said.

Passenger Joe Frank, 20, who was returning from Texas with his sister, said the plane dropped violently and he heard a loud bang, followed by screams.

Frank said he wasn’t wearing a seatbelt and was thrown to the ceiling, banging his head. He found out afterward that a baby in a seat one row back had been propelled out of its parent’s arms and landed safely on an empty seat across the aisle.

“As we levelled off you heard a father cry out, ‘Where’s my baby?’ That’s when I turned around and heard a guy say, ‘It’s right here,’” Frank said.

Old Bull said that when the plane finally quieted, he saw a frightened-looking man poke his head out the door of a nearby restroom and then crawl out, clutching at an armrest to keep his balance.

A spokesman for the National Transportation Safety Board said the agency was gathering details on the severity of injuries and whether there was any damage to the aircraft. That information will determine if a full-scale investigation is warranted, said NTSB spokesman Terry Williams.

During the last decade about 33 people annually were injured during turbulence on airplanes, with crew members suffering most of the injuries, according to information from the Federal Aviation Administration.

Turbulence is caused by air movements created by weather events such as thunderstorms, cold or warm fronts and air moving around mountains, according to the FAA. It can occur unexpectedly and when the sky appears clear.

Authorities say staying buckled up is one of the easiest ways to prevent injuries.