A police van on Monday overturned in a collision with a double-decker bus, a car and a delivery van in Tseung Kwan O, injuring at least six people.Eight people climbed on the police van to help the officers trapped inside before emergency crews arrived. Seven fire engines and seven ambulances were dispatched to the scene on Po Lam Road North near Hong Sing Garden before, according to the Fire Services Department. The van was from the Tseung Kwan O police division.A spokeswoman for the fire…