HERAT, Afghanistan — A fuel tanker exploded on the Afghan-Iranian border on February 13, causing a massive fire and a chain reaction that destroyed more than 500 trucks carrying natural gas and fuel.

Afghan officials and Iranian state media said the blast occurred on the Afghan side of the border in the western Afghan province of Herat at the Islam Qala border crossing.

Wahidullah Tawhidi, a spokesman for Afghanistan’s Ministry of Power Supply, said the blaze forced Afghanistan to shut down its electrical supply from Iran — leaving the provincial capital of Herat in darkness after nightfall.

Initial reports said at least seven people were injured. But Wahid Qatali, Herat’s provincial governor, suggested the number of casualties could be much higher — saying:: ““For the time being, we can’t even talk about the casualties.”

Qatali said it wasn’t immediately clear what caused the explosion. He said Afghan firefighters did not have the means to put out the enormous blaze and had requested support from Iran in the form of firefighting aircraft.

Mohammad Rafiqu Shirzy, a spokesman for the regional hospital in the city of Herat, said the intensity of the flames meant ambulances were having trouble reaching the wounded or getting close to the site of the blast.

But he confirmed that at least seven people injured by the fire had been admitted to the hospital in the city of Herat, about 120 kilometers east of the border.

Iran’s semiofficial ISNA news agency quoted truck drivers who said that more than 500 trucks carrying natural gas and fuel were burned.

The Associated Press reported that two explosions at the border crossing were powerful enough to be spotted from space by NASA satellites.

The first was at about 1:10 p.m. local time and the next was about half an hour later.

The fire was continuing to burn after nightfall.

The road between the city of Herat and Islam Qala is a dangerous stretch of highway that Afghans rarely travel on during the night for fear of attacks by criminal gangs.

Taliban militants also travel freely in the area. Afghan security services had set up checkpoints and were assisting ambulances and emergency vehicles traveling to and from the border crossing.

Iran’s state-run IRNA news agency quoted Mohsen Nejat, director-general of crisis management in Iran’s Khorasan Razavi Province. as saying that Iranian “rescue forces and fire fighters were under way to extinguish the fire inside Afghanistan” at the request of Herat’s provincial governor.

Iranian state television reported that fire also spread to the Dogharoon customs facilities on the Iranian side of the border.

It reported that Iranian firefighters, troops from the Iranian Army, and Iranian border guards were all working to try to extinguish the blaze.

Other trucks carrying natural gas and fuel were directed to leave the scene.

The United States allows Afghanistan to import fuel and oil from Iran as part of a special concession that exempts Kabul from U.S. sanctions against Iran.

Satellite photos taken on February 13 before the explosion showed dozens of tankers parked at the border crossing.

With reporting by AP, Reuters, AFP, and Tolonews.com