Dozens of passengers were forced to stand on the wing of an American Airlines plane at Denver International Airport as they evacuated the aircraft after one of its engines caught fire Thursday evening, sending thick black smoke billowing into the air.

This is the latest incident in a spate of alarming aviation disasters and close calls which have stoked worries among flyers.

American Airlines Flight 1006, a Boeing 737-800 en route to Dallas-Fort Worth from Colorado Springs with 172 passengers and six crew aboard, diverted to Denver around 5:15 p.m. local time, after the crew reported “engine vibrations,” the Federal Aviation Administration said in a statement.

“After landing and while taxiing to the gate an engine caught fire,” the statement said.

The FAA and the National Transportation Safety Board are investigating the incident.

Shortly before landing, the plane’s pilot notified air traffic controllers in Denver that the flight was experiencing engine issues, but it was not an emergency, according to air traffic control audio from LiveATC.net.

“American 10,006, uh, 1006 just to verify not an emergency still, correct?” the controller asked.

“Nah, we just have a high engine vibration so we are cruising slower than normal,” the pilot responded.

The situation appeared to quickly escalate several minutes later, after the plane landed, when someone on the radio yelled “Mayday, Mayday, Mayday! Mayday! … engine fire!”

The plane arrived at gate C38, a Denver International Airport spokesperson told CNN. The fire was extinguished and all passengers were evacuated, the spokesperson said.

Images from the scene show dozens of passengers exiting the aircraft and standing on the wing as smoke filled the air. Some passengers evacuated the plane on a slide, video published by Reuters showed.

Twelve passengers were taken to the hospital with minor injuries, Denver Fire Department told CNN. All have been released, according to American Airlines.

“We thank our crew members, DEN team and first responders for their quick and decisive action with the safety of everyone on board and on the ground as the priority,” American Airlines said in a statement.

‘Everyone started screaming’

Passenger Ingrid Hibbits described the panic and flames when the engine caught fire.

“Everyone started screaming, and you hear, ‘Fire!’ Hibbits told CNN affiliate KTVT.

When she looked out the window, she saw flames and the window “bubbling, like melting,” Hibbits said.

“Everybody was kind of pushing to get out of the plane,” she said. Eventually, Hibbits evacuated the cabin and stood on the plane’s wing.

Hibbits said she panicked because she was separated from her family. While Hibbits was in the middle of the plane, her two daughters were toward the front, and her husband was toward the back.

Another passenger, Michele Woods, told KTVT she noticed one engine sounded louder than the other when the plane took off.

When the plane diverted to Denver, everything seemed fine – until the plane landed, Woods said.

“Smoke started to fill the cabin, and people started screaming and pushing and jumping and yelling,” Woods told KTVT. “People were saying, ‘Don’t push, don’t push.’”

Woods said she tried to calm two young girls next to her.

“I was just like, ‘Don’t worry about your bags, you don’t need your bag,’” Woods told the girls. “Let’s just get off the plane.”

‘I was terrified for those passengers’

Video captured by a Montana woman inside the airport waiting for a connecting flight shows a large cloud of smoke emanating from the plane and dozens of passengers running away.

Kristal Leonard, who was flying in from Helena, Montana, told CNN she was waiting inside the Denver airport for her connecting flight to Colorado Springs. That’s when she looked outside and saw flames and smoke engulfing the plane.

“I was terrified for those passengers,” Leonard said. “I can’t even imagine how scared they must’ve been.”

Ground crews appeared to extinguish the fire relatively quickly, according to a video filmed by a passenger inside the airport. Footage shows bright orange flames and black smoke disappearing and turning into a misty white haze as workers put out the fire.

American Airlines is sending a replacement aircraft and crew to Denver to help customers continue on to Dallas, the airline said.

A preliminary report will be ready in a month

The NTSB said it was sending “two investigators with expertise in commercial aircraft and powerplants” Friday.

“Once on site, the investigators will begin the process of documenting and examining the aircraft, conducting witness and crew interviews, and obtaining other data that could contain information relevant to the investigation,” the NTSB said in a statement.

“A preliminary report will be available within 30 days; it can be accessed by searching our investigations database with the NTSB number DCA25FA159,” the agency said.

“The preliminary report will contain factual information gathered during the initial phase of the investigation. A probable cause of the event along with any contributing factors will be detailed in the final report, which is expected in 12-24 months.”

A spate of high-profile crashes

Thursday’s plane engine fire comes just three weeks after a Delta Air Lines flight crashed, turned upside down and caught fire on the runway at Toronto Pearson International Airport.

That incident was preceded by deadly crashes this year in Alaska, Philadelphia, and Washington, DC, where an American Airlines plane collided midair with a US Army Black Hawk helicopter in January, killing 67 people.

In December, aviation disasters in South Korea and Kazakhstan killed more than 200 people.

This story has been updated with additional information.