KARACHI, Pakistan -- A Pakistani government official says a road accident has killed at least 20 people, including 18 schoolchildren in the country's south.

Deputy Commissioner Aleem Lashari says a school bus on a day trip collided head on with a garbage truck in Nawab Shah district on Wednesday.

He also says 19 people, including 15 children, were injured in the crash.

Lashari says it's not yet clear what had caused the accident. He says the place where it occurred has a sharp turn, which has caused accidents in the past.

Bad road infrastructure and poor driving often cause accidents in Pakistan.

Government minister Sharjeel Memon says authorities are investigating.