Venomous and highly invasive fire ants have been found at Osaka port, with the first confirmation of a queen ant in the country, the Environment Ministry said.

The discovery is serious as queen ants can lay over 1,000 eggs a day. While no eggs have been found, the ministry is looking into whether the ants have built a nest.

The discovery, announced Tuesday, came during a probe conducted after another venomous alien ant species was found in a container that had reached a warehouse in Suminoe Ward in the city of Osaka on Thursday. The container had been shipped from Hong Kong.