Calderdale Council said: "There's been a serious road traffic incident at King Cross, Halifax.
"Please avoid the area completely to allow emergency services to respond."
The Yorkshire Tiger bus company said just before 6.30pm that Rochdale Road at King Cross was closed due to a an RTA (road traffic accident), thought to have happened in the early hours.
The area has been cordoned off by police and there were numerous emergency vehicles at the scene.
Pictures seen by the YEP show at least two cars at the scene, one of which was very damaged.
Yorkshire Tiger services were being diverted down Burnley Road.