Italian police arrested six individuals suspected of smuggling oil into the country from Libya, Reuters reports.

Arrest warrants have been issued for three others.

Authorities believe that the smuggling ring sold at least 30 million euros worth of Libyan diesel in Europe, Reuters reports.  The diesel was stolen from the National Oil Corporation’s refinery in Zawiya.

Italian authorities believe that more than 80 million kilos of diesel were smuggled into the country, according to Reuters.

Earlier this month, Libyan media reported that the country’s coast guard had fired on a suspected oil-smuggling vessel.

Libya has struggled to maintain security at its oil production facilities. Over the past few months, its oil industry has suffered repeated setbacks due to poor security.

The NOC is Libya’s state-run oil company.