A United Airlines flight experienced an engine fire shortly after takeoff that was apparently caused by a rare rabbit strike.
United Flight 2325 had departed Denver International Airport en route to Edmonton, Alberta, on Sunday when the incident occurred.
LiveATC audio documents the flight crew asking that the plane be inspected for an engine fire and being told that it was a rabbit that apparently got sucked into an engine.
"Rabbit through the number 2, that'll do it," the pilot responded.
The Boeing 737-800 was carrying 153 passengers and six crew members.
"There was a loud bang, and a significant vibration in the plane," passenger Scott Wolff told "Good Morning America."
The plane proceeded to climb, Wolff said.
"Every few moments there was a backfire coming from the engine, a giant fireball behind it," he said. "Everyone in the plane then started to panic."
MORE: American Airlines flight diverts to JFK after apparent bird strike damages engineWyatt McCurry saw the flames from the ground at the Denver airport.
"My stomach dropped and I just thought, 'I'm going to see a plane go down,'" he told "Good Morning America."
The flight safely headed back to Denver.
"Our flight from Denver to Edmonton (UA2325) returned safely to Denver to address a possible wildlife strike," United said in a statement.
The Federal Aviation Administration said the plane returned around 8:05 p.m. local time on Sunday "after the crew reported striking an animal while departing."
The passengers continued to Edmonton on a new aircraft, the airline said.
MORE: Security scare that led to diverted flight was hoax by 2 young children: FBIThe FAA is investigating.
In general, wildlife strikes are fairly common, with the FAA reporting more than 20,000 in the United States last year.
Among those, there were only four rabbit strikes reported, including one at the Denver International Airport, according to the FAA. The vast majority are bird strikes.