BRASILIA, Brazil (AFP)—A head-on collision between a bus carrying medical patients and a truck killed at least 23 people early Wednesday in southern Brazil, highway police said.

The crash occurred at 3:30 am local time (6:30 GMT) when the truck veered into the other vehicle’s lane in the municipality of Ipiranga in Parana state, police said.

“At least 23 deaths have been confirmed. Most of the victims were on the bus,” authorities said in a press release. The truck driver was among those killed.

Images in the local press showed the bus smashed to pieces next to a truck at the roadside.

Initially, the company that manages the highway said the accident took place in Imbituva, where the bus began its journey.

The collision occurred on a highway that connects the southern part of the country with Sao Paulo, Brazil’s wealthiest state.

Hours later, the highway remained closed, causing a miles (kilometers)-long backup of vehicles.

The bus belonged to the Imbituva health department and was transporting patients to medical centers in the city of Curitiba.

Authorities have not provided any information about the truck’s occupants.

Fatal traffic accidents are common in Brazil.

Eight people died on Sunday in the state of Rio de Janeiro when the bus they were traveling in overturned.

In February, a bus returning from a religious festival in northeastern Brazil veered off the road and overturned, killing at least 16 people.