MIAMI -- There was quite a scare for passengers on an American Airlines flight out of Miami.

On Tuesday, Flight 1640, a Boeing 757, experienced a sudden loss of cabin pressure. According to the airline, the Boston-bound flight had 154 passengers and six crew members aboard.

The incident occurred at 31,000 feet and oxygen masks automatically deployed.

The crew declared an emergency and were able to bring the plane down safely. The plane has been taken out of service.

The cause of the problem is still unknown, but investigators found a hole in the plane. The hole was over the front door of the Boeing 757-223 where passengers typically enter. American Airlines described the hole as small, roughly one foot by two feet.