TEHRAN – At least 19 people died and 27 were wounded in a collision overnight involving a passenger bus and diesel tanker truck in central Iran, official sources said on Tuesday.

Many of the bodies had been burned, making the dead difficult to identify, according to the head of traffic management for the nearby city of Natanz, as cited in the semi-official ISNA news agency.

Flames and smoke were seen rising from the crash site as rescue crews worked with heavy equipment, in an image taken from video footage made available to EFE by Iranian state television.

The bus crashed shortly before midnight on Monday while traveling from the capital Tehran to the southeastern city of Kerman, ISNA reported, adding that the truck driver survived but the bus driver did not, making the cause of the accident still uncertain.

Iranian President Hassan Rouhani ordered an investigation into the crash, the state-run IRNA news agency said Tuesday.

Traffic accidents are highly common in Iran, and caused over 16,000 deaths in the Iranian government’s most recently-available statistical year, which ended in March 2017.