BUDAPEST, Hungary (AP) -- Firefighters in Hungary have contained a blaze that broke out overnight at the country's main oil refinery, authorities and Hungarian energy company MOL said Tuesday. No injuries have been reported.

The fire erupted Monday night in a processing unit of the Danube Refinery in Százhalombatta, south of the capital Budapest, MOL said in a statement posted to the Budapest Stock Exchange website Tuesday. The cause of the incident is under investigation.

MOL said emergency protocols were followed and units not affected by the blaze were being gradually restarted as damage assessments continued. The company added that it would focus on ensuring domestic fuel supplies and was considering whether to draw on Hungary's strategic reserves.

Prime Minister Viktor Orbán said on Tuesday that he had spoken with MOL executives and the interior minister about the fire. "Hungary's fuel supply is secure," Orbán wrote on social media, adding that the circumstances surrounding the blaze were being investigated "as thoroughly as possible."

The refinery in Százhalombatta, Hungary's only major crude-processing facility, refines primarily oil sourced from Russia -- a rarity in the European Union since the bloc's countries moved to slash their imports of Russian oil and gas after Moscow launched its invasion of Ukraine in February 2022.

The EU instituted an embargo on Russian oil shortly after the start of the war and, this year, announced a proposal to gradually stop the import of all Russian gas and oil into the bloc by the end of 2027.

Yet as the rest of Europe has weaned off Russian energy, Hungary has maintained, and even increased, its Russian imports, insisting no viable alternative exists.

On Tuesday, authorities said air quality around the refinery was being continuously monitored and no readings above health limits had been detected.

According to Hungary's disaster management authority, the facility's own fire brigade was first on the scene, supported by professional firefighters from nearby cities.

Eyewitnesses told the state news agency MTI that flames and smoke were visible from several kilometers away.