WARSAW, June 18 (Xinhua) -- Two persons were killed and 16 injured in a bus accident in mid-northern Poland on Monday morning.

According to the Polish Press Agency, the bus, which carried around 50 passengers, fell into a ditch and turned over.

Two helicopters and several ambulances were sent for the rescue operation, which is still going on.

The mishap blocked Road No. 91, which connects two major cities - Gdansk and Lodz. The police are arranging detours.