Police were called to the village of Bricket Wood in Hertfordshire to investigate reports of gunfire in the early hours of Monday morning.However, they discovered the noise was actually coming from the set of the action show, 24: Live Another Day, which was being filmed in a former government research building.More than 20 calls to emergency services were made by panicked residents.Sarah Spence, spokeswoman for Hertfordshire Constabulary, said; "We were called at around 2am to reports of gunfire being heard in the Bricket Wood area. Officers were in attendance. "However, there was no incident. It was confirmed some sort of filming was taking place. Normally, we would be contacted to say filming would be happening in the area."Representatives for the Fox network insist letters were sent out to local residents to inform them about the filming.