Iranian forces are reported to have detained two tankers in the Gulf over allegations of fuel smuggling.

The two vessels and 15 foreign crew members were detained on suspicion of being involved in fuel smuggling operations in the waters around Farsi Island, the Islamic Republic News Agency reported on Thursday, citing information from the IRGC Navy.

One of the vessels is reported to be holding more than one million liters of smuggled fuel.

The detentions follow investigation of the vessels’ activities over a period of months, according to the report.

The news comes amid heightened tensions between the US and Iran over the possibility of negotiating a new nuclear agreement.