London (Reuters): A mouse caused a big delay for a flight from London to San Francisco , forcing passengers to switch aircraft after the tiny mouse was discovered from the plane.

San Francisco media reported that the mouse was spotted running through a door aboard British Airways Flight 285 at London's Heathrow Airport on Wednesday as passengers were fastened their seat belts for departure.

This forced them to switch aircraft and endure a four-hour delay .

Some passengers joked that the mouse lacked a visa to enter the United States, according to passenger Annina Salven, who laughingly told KGO it made sense to switch planes "because I really wouldn't want to eat food on a plane that had a mouse ."

Rodents have been known to chew through the wiring on aircraft, with potentially dangerous results.

British Airways in a statement confirmed the disruption of its Flight 285 from London's Heathrow Airport to San Francisco , saying "on this occasion there was one very small customer who we had to send back to the gate."