Five Japanese and three Chinese men were arrested Thursday for allegedly smuggling 206 kg of gold by ship into a port in Kyushu, law enforcement authorities said. If verified, it would be Japan's largest gold-smuggling case ever.

The local customs house is trying to verify that the cargo, which was seized Wednesday at Nagoya port in Karatsu, Saga Prefecture, is actually gold. It was not immediately known if the suspects had confessed yet.

Japan's largest gold seizure to date weighed 130 kg and was smuggled by air to Osaka's Kansai International Airport in February 2015, according to the government.

The eight men arrested Wednesday on suspicion of breaching the customs law include Yasuaki Saito, 49, from Iki in the neighboring Nagasaki Prefecture, and Kenichi Kinoshita, 65, from Miyagi Prefecture, according to the police and the local coast guard.

The authorities received information that a suspicious ship once registered in Aomori Prefecture was berthed at a port in Nagasaki. The 19-ton vessel had once been registered as a fishing boat in Aomori, investigators said.