Vietnam wants its importers to ensure that what they’re bringing into the country won’t contain a disputed South China Sea map that’s been spotted in items from vehicle navigation to solar inverter software.

The Ministry of Industry and Trade, in a statement on the website, said companies must review contracts and improve their monitoring of the imported goods. For high risk items like maps, publications, gadgets, importers must ask sellers for a “written commitment” that none of the products violate Vietnam’s sovereignty.

Companies must immediately report any suspected violation to provincial authorities, it said. Earlier this month, Vietnam said it will fine Volkswagen AG’s local distributor and a car importer over a navigation app reflecting China’s nine-dash-line claims. Solar power inverters were also found using a software that refer to the disputed map.

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Southeast Asian countries have clashed with China over maritime claims in the region, where Beijing’s nine-dash-line encompasses waters the U.S. has said could contain unexploited hydrocarbons worth $2.5 trillion. Vietnam and China fought a war along their land border in 1979.