Eleven people were killed and six others injured Monday when a bus ran off the road in a mountainous area of Brazil's Rio de Janeiro state, first responders said.

The accident took place near the town of Guapimirim on the highway linking Rio de Janeiro city with Teresopolis.

The vehicle left the town of Itaperuna, in northwestern Rio state, early Monday with 29 people aboard, the Auto Viação 1001 bus company said.

Authorities are still trying to determine what caused the bus to run off the road while rounding a curve and then plunge into a wooded area. EFE