The Boeing 737-800, carrying 109 people, was roughly halfway through its flight from Miami to the Caribbean island of St. Lucia when it landed at the airport in Providenciales.

“I know that they landed because of the smell of fumes of cabin. That had to be checked out,” said Peter Forbes, deputy managing director of the British territory’s civil aviation authority.

It was unclear what released the fumes that alarmed the flight crew. Everyone aboard the plane was evacuated safely at the airport and mechanics were evaluating the aircraft, Forbes said.

American Airlines did not immediately respond to a request for comment.