HANOI, Jan. 14 (Xinhua) -- Four people were killed and six others injured in a traffic accident on the Thanh Hoa-Hanoi Expressway in central Vietnam's Thanh Hoa province, local media Tuoi Tre reported Wednesday.

The incident occurred at about 3:40 a.m., involving two tractor-trailers and a 15-seat passenger coach, the report said. All vehicles were damaged in the collision.

Further investigation is underway into the cause of the accident. ■