"Negotiators and a tactical response team are at the scene and trying to gain access to the building," a police spokeswoman told Sky News.
The wounded have been delivered to Liverpool Hospital, where one is undergoing surgery and another is being treated for less threatening injuries; both are under police guard. Ambulances and emergency crews have also been deployed at the scene. The police have advised the public not to venture within one kilometer of the factory.
According to the broadcaster, the witnesses heard up to five shots. Other sources have suggested that hostages may have been taken during the shooting.