Sixty people, including a deputy mayor, have been punished for a serious expressway accident involving a bus that killed 36 people in August.

Among those punished, 28 people, including the bus contractor, Nie Dianzhou, are being investigated by police and prosecutors, the State Administration of Work Safety said in a statement on Wednesday.

The other 32 people, including Zhang Shimin, deputy mayor of Luoyang, Henan province, where the bus was registered, was reprimanded.

The accident occurred in the city of Ankang, Shaanxi province, when a packed bus carrying 49 people hit the wall at the mouth of an expressway tunnel on the Xi'an-Hanzhong section of the Beijing-Kunming Expressway on Aug 10.

At least 36 people were killed and 13 others injured in the accident, resulting in 35.3 million yuan ($5.6 million) in direct economic losses.

The direct causes of the accident were speeding and driver fatigue, the statement said.

The driver, Wang Baiming, had been driving nonstop for more than 35 hours before the accident and only had a two-day rest in the 38 days leading up to the accident. He was driving 80 to 86 kilometers per hour in a section with a speed limit of 60 km/h, according to the State Administration of Work Safety. Wang was killed in the accident.

With a designed carrying capacity of 51 people, the bus was en route from Chengdu, Sichuan province to Luoyang.