A policewoman was under investigation today after her machine gun went off while she was unloading it at Mong Kok police station. A bullet from the Heckler & Koch MP5 submachine gun slammed into the wall after discharging in the station's loading bay on Prince Edward Road at 3pm yesteray. "One shot was fired damaging a wooden partition," a senior police officer told the SCMP . "The policewoman was unhurt." He said an internal probe had ben launched to investigate whether the officer, attached to the Kowloon West emergency unit, had been following proper guidelines over the use of firearms when the gun went off. "Disciplinary action will be taken if results of the investigation indicate the incident involved human negligence," he said. He added that it was rare for an MP5 weapon to discharge accidentally. Officers from the Operations Wing of Kowloon west regional headquarters are conducting the investigation. On their website German firm Heckler & Koch describe the MP5 as: "Tremendously reliable, with maximum safety for the user, easy to handle, modular, extremely accurate and extraordinarily easy to control when firing... features that are particularly appreciated by security forces and military users worldwide." It adds: "There are now well over 100 variants of the MP5 available to cover the large number of different tactical requirements for a wide variety of users. whether on land, on the water or in the air – the MP5 is universally applicable, making it usable in all areas and under all conditions."