An accidental explosion in a chemical tanker killed 18 people and injured 40 others at Hyderabad in the southern Pakistani province of Sindh on Monday, police said.
The explosion occurred in the tanker parked outside a scrap depot near a transport hub in Hyderabad, located 160 km north of Karachi.
"It was an accidental blast caused by a gas cylinder," city police chief Javed Alam told mediapersons.
Most of the casualties were caused by parts of the truck, which was carrying 30,000 litres of "thinner".
The truck exploded after gas pressure built up in a storage tank, police said.
Footage on TV news channels showed hundreds of people crowding the blast site and searching through the rubble of destroyed shops for the dead and injured.
Security forces cordoned off the blast site and an emergency was declared in the local hospitals.
Hospital officials described the condition of nine of the injured as critical.
Several trucks and houses and a mosque were damaged by the blast. Power pylons were also damaged and power lines were snapped.
Sindh Home Minister Zulfikar Ali Mirza told the provincial assembly that the blast was not caused by a bomb and there was no evidence of a sabotage.
Authorities were trying to determine the exact cause of the blast, he said.