ISLAMABAD — A fiery crash between an oil tanker and a passenger bus killed at least 20 people in Pakistan, a police spokesperson and media said on Tuesday.

It was not immediately clear what caused the crash late Monday night or early Tuesday on a motorway near the central city of Multan, Reuters reports.

The bus and tanker caught fire after the collision, a police spokesperson said in a statement, without providing details on the number of fatalities.

Geo and Dunya TV reported at least 20 people were killed.

Six passengers survived, an official of a state-run rescue service told Dunya TV on the spot.

"The fire was raging when we got here," he said. — Agencies