The accident occurred on Monday on Highway 191 in the municipality of Ipeuna, 206 km from Brazil's largest city Sao Paulo, Xinhua news agency reported.

One bus was taking patients to a medical center for clinical studies while the other vehicle was empty.

Four of the victims were traveling in a bus carrying patients. The fifth casualty was the driver of the empty bus.

Local officials said that as a result of the accident, the highway was closed in both directions to facilitate rescue efforts.