LISBON, Portugal -

At least 10 people are dead and 32 are injured after a bus crash in Portugal.

A National Guard spokesman says the bus went off the highway and flipped several times before ending up in a deep ravine.

Television images showed a large rescue operation mounted on the rain-soaked approach road, including more than 260 firefighters and at least one rescue helicopter.

Young children and middle aged couples were among the passengers on that bus.

Officials are still unsure about what caused the bus to go off the road.