Passengers on a San Francisco bound British Airways flight from London Heathrow on Wednesday suffered a four-hour delay due to the discovery of a mouse on the plane.

The British Airways' Flight 285 operated by a Boeing 777-300, was readying to push back from the boarding gate when the mouse drama began.

"Somebody saw a mouse that scurried under one of the doors," passenger Chris Claeboe said to ABC 7 of San Francisco. "They kept us on the plane for about 15 minutes, told us we had to get off the plane because we couldn't fly with a mouse."

Eventually, passengers on BA Flight 285 were put on a replacement aircraft, causing a delay of 4 hours and 16 minutes, according to British Airways’ website.

The flight made up some time en route but still landed in San Francisco late, arriving 3 hours, 35 minutes past schedule.

British Airways acknowledged the disruption in statement provided to Today in the Sky.

"With service and prices this good, we know almost everyone wants to fly with us to San Francisco," the carrier said. "But on this occasion there was one very small customer who we had to send back to the gate. Everyone holding their own passport is now on their way to California, and we are sorry for the delay."