WELLINGTON (Reuters) - South Pacific island nations are scouring shipping records for vessels with links to North Korea after Fiji said it had identified 20 falsely flagged ships it suspects the isolated regime is using to evade United Nations sanctions.

Fiji, along with Interpol and the Singapore-based regional shipping regulator Tokyo MoU, are investigating the vessels for links to North Korea, a spokesman for the country’s Maritime Safety Authority (MSAF) told Reuters on Friday. Interpol and Tokyo MoU did not immediately respond to requests for comment on their investigations.

The 18 members of the Pacific Islands Forum this month agreed to launch an audit of every ship registered in the Pacific to search for any links to North Korea.

New Zealand Foreign Affairs Minister Gerry Brownlee said Pacific countries, including his own, were concerned North Korea was using falsely flagged cargo ships as one avenue to trade goods in spite of sanctions.

“What we do know is that declared North Korean GDP (gross domestic product) is not big enough to support the nuclear program that they’re running so there has to be significant black market or offbook revenue going into the country,” Brownlee told Reuters in a phone interview this week.

The move came as the UN on Monday ramped up sanctions on North Korea, including tightening up oversight of vessels on the high seas. Authorities will now be allowed to check suspected vessels for prohibited cargo with the authority of the flag country.

UN sanctions introduced in August banned North Korean exports of seafood as part of efforts to curtail the regime’s access to foreign funds.

North Korea had been expected to earn an estimated $295 million from seafood in 2017, one U.N. diplomat said.

In Fiji’s case, the North Korean-linked ships had adopted the island nation’s flag without formally registering, the MSAF said.

It was not known in what way the possibly more-than 20 vessels were linked to North Korea or what their suspected activities or locations were. The MSAF declined to provide details due to the ongoing investigation.

In addition to the fraudulent use of flags, Pacific governments were concerned North Korean vessels could be quietly registering in nations that allow international ships to use their flags.

“If it’s not clear why they’re on that register, in other words, they’re not regular callers into Pacific ports, then further investigation is needed to untangle the ship owner,” said Brownlee.

The review would take place over the next couple of months, Brownlee said, and Australia and New Zealand would provide intelligence to help the small island nations check any North Korean connections.