A massive fire at an oil refinery near Iran’s capital burned into a second day Thursday as firefighters struggled to extinguish the flames.

The fire began at the state-owned Tondgooyan Petrochemical Co. to the south of Tehran on Wednesday night, sending a huge plume of black smoke into the sky over the capital.

The Oil Ministry’s SHANA news agency said the fire broke out over a leak in two waste tanks at the facility. Authorities initially suggested the flames affected a liquified petroleum gas pipeline at the refinery.

Iranian Oil Minister Bijan Zanganeh visited the scene overnight. While seeking to assure the public the fire wouldn’t affect production, Iranians queued up for gasoline on Thursday morning, the start of the weekend in the Islamic Republic.

SHANA also quoted refinery spokesman Shaker Khafaei as saying authorities hoped the fire would extinguish itself after running out of fuel in the coming hours.

It wasn’t immediately clear what started the blaze. Temperatures in Tehran reached nearly 40 degrees Celsius (104 degrees Fahrenheit) on Wednesday. Hot summer weather in Iran has caused fires in the past.

The blaze came the same day a fire struck the largest warship in the Iranian navy, which later sank in the Gulf of Oman.

(AP)