Environment Minister Masaharu Nakagawa called on China to take measures to prevent the international spread of fire ants, which have repeatedly been found in shipping containers from China over the past year.

Nakagawa made the request Saturday in a bilateral meeting with his Chinese counterpart, Li Ganjie, on the sidelines of a trilateral meeting of environment chiefs in Suzhou, China, that included South Korea.

More than 2,000 of the invasive, stinging ants were found in a shipping container at a port in Osaka Prefecture earlier this month after it arrived from China. The discovery was the latest in Japan, which has seen the ants, which are native to South America, turn up in 12 prefectures including Tokyo since they were first discovered in May 2017 in Hyogo Prefecture after arriving in another container from China, according to the ministry.

In response to Nakagawa’s request, Li said his ministry is working with relevant departments to maximize efforts against the outbreak, which originated in South America.

Japan is asking for ant bait to be placed inside China’s shipping containers, but China expressed reservations about using such a solution.

In the meantime, the Japanese Environment Ministry and the Chinese Ecology and Environment Ministry signed a memorandum of understanding to accelerate cooperation over the next three years to address air pollution.

Nakagawa also met with South Korean counterpart Kim Eun Kyung and raised the problem posed by polyethylene tanks with Korean markings washing up on the coast of the Sea of Japan. After requesting that preventive measures be taken, Kim said her side would take action.

The trilateral meeting, which has been held annually in rotation since 1999, will wrap up Sunday with a joint statement.

Fire ants are famed for their burning sting, which in severe cases can cause anaphylaxis and even death in sensitive individuals.