A fire at an Iranian refinery in Tehran killed six workers and injured two more, Iranian state-run media reported, according to Reuters.

The incident was apparently caused by a technical issue.

“Unfortunately technical problems caused leakage of oil that led to explosion and fire, the local governor,” Hedayatollah Jamalipour told local media, according to Reuters.

The incident is currently under investigation, Mehr News Agency reports.

It is unclear if operations at the refinery will be impacted.

Years of sanctions against Iran’s oil industry degraded the capacity of Iran’s refineries. After the lifting of sanctions as part of its nuclear agreement with members of the international community, Iran has sought foreign investments to modernize its refining operations, Hellenic Shipping News reported earlier this year.

Iran’s South Pars refinery has been offline recently due to maintenance work at the facility, according to Zawya.