Delta Boeing 767-332ER taxiing towards the airport runway

A New York-bound Delta Air Lines flight was evacuated in Madrid, Spain after smoke began to fill the cabin prior to takeoff on Tuesday.

No injuries were reported but passengers were delayed for two hours, according to flight-tracking website FlightAware.com.

The smoke was believed to have been the result of oil dripping onto an auxiliary power unit.

“The @delta plane got on fire in the back. There was smoke everywhere,” a passenger wrote in a Twitter post. “They waited to see what it was until they let us out of the plane. I have not stopped coughing. Don’t understand why they didn’t let us get off the plane right away.”

Delta confirmed the evacuation and apologized to customers in a statement to Fox News.

“We apologize to customers of flight 127 from Madrid to New York–JFK, as the crew elected to deplane the aircraft due to a smoky odor detected in the cockpit and cabin,” a spokesperson told the news outlet. “Customers safely exited the aircraft, which was still at the gate and were then re-accommodated to their final destinations. We are working to reach out to these customers individually as we extend our apologies.”

The airline said that its maintenance teams investigated the incident before the plane was returned to service.

Delta is now in the process of reaching out to customers to provide compensation for the inconvenience. Last year, Delta awarded a passenger 15,000 bonus miles after he was delayed for a smoky odor in the cabin.