RIO DE JANEIRO, Dec. 22 (Xinhua) -- At least 14 passengers were killed early Sunday morning when a bus fell into a ravine in Sao Lourenco da Serra municipality, the Federal Highway Police said.

The bus with 54 passengers on board was en route from Curitiba, in the southern state of Parana, to Rio de Janeiro. It fell into a ravine at some 50 km from Sao Paulo, the largest city in Brazil and South America at 2:30 a.m. local time Sunday.

So far, the causes of the accident have not been identified, but the authorities suspected that the driver fell asleep.

According to the police, the driver, who was injured, admitted that there was no mechanical problem or anything in the pavement that could cause the accident.

Other 12 people, including one baby, were injured in the accident. The injured people were taken to nearby hospitals.