One person died and 20 others were injured when a passenger bus plunged into a roadside stream after hitting a motorcycle in the southern province of Dong Nai on Wednesday.

The bus with 29 passengers onboard was traveling on National Highway 20 through Dong Nai's Thong Nhat District when a motorist suddenly crossed the road.

The bus driver tried to pull over but he could not make it and crashed into the motorcycle.

Following the crash, the bus plunged into a roadside stream, turning on its side.

Nguyen Thanh Tam, the motorcyclist, died on the spot.

Twenty passengers in the bus were injured, four of them seriously.

The accident caused a gridlock on the highway for hours. Local traffic police sent three cranes to the site to tow the bus away.

Authorities are investigating the accident.