A crowded bus tipped over a bridge and crashed into a river in central Vietnam, killing 34 people and injuring 20, some of them in serious condition, Vietnam authorities said.

The bus smashed through the rails of the bridge Thursday night and plunged into the bank of the Serepok River about 18 meters (60 feet) below, the Associated Press reported citing local officials.

The bus was en route to the southern commercial hub of Ho Chi Minh City, on a regular 350-kilometer (217-mile) trip from the central highland province of Dak Lak.

Local authorities are in the process of investigating the cause of accident and identifying the fatalities.

Two drivers of the bus were among the 32 people who died at the scene, Y Bliu Arul, deputy director of the General Hospital in Dak Lak, was cited as saying. Two others died at the hospital.

Sixteen among the 21 injured were in serious condition. The front of the bus was submerged and deformed, making it hard for the rescue work, a Reuters report said.

Road accidents kill about 35 people in Vietnam every day, according to a Bangkok Post report. Narrow highways, poorly maintained vehicles and disregard for traffic rules are considered the reasons for most accidents.