More than 2,000 venomous fire ants have been discovered in a shipping container from China that arrived at a port in Osaka Prefecture earlier this month, leaving two people hurt, government officials said Saturday.

The discovery Friday of the invasive species native to South America is one of the largest in Japan, on a par with the estimated 2,000 fire ants discovered in Muko, Kyoto Prefecture in October last year, the Environment Ministry said.

(Photo courtesy of the Environment Ministry's Kinki Regional Environment Office)

The ants in Osaka and Kyoto have since been exterminated.

Fire ants have turned up in 12 prefectures including Tokyo since they were first discovered in May 2017 inside a container that was shipped from Guangzhou, China and unloaded in Amagasaki, Hyogo Prefecture, according to the ministry.

In the latest case announced by the ministry and Osaka city government, two workers were stung by the fire ants and complained of swelling and pain, although they did not require hospital treatment.

A queen ant was not found.

The authorities said the container left Shenzhen, China, on June 5, and arrived at the Osaka port on June 12 via Hong Kong. It was transported two days later to Kishiwada, Osaka Prefecture by land.

On Friday, about 100 fire ants were found while the cargo was being unloaded. One of the workers involved was stung on his back and left hand, prompting his employer to report the incident to the ministry.

After investigating the container, the city and ministry found a large number of fire ants that were alive.

The ants were exterminated, and to prevent any further spread, insecticide was sprayed but during the process, a ministry employee was stung on his left hand. An expert confirmed on Saturday that the species were indeed fire ants.

Fire ants are known for their sting, which can cause anaphylaxis, a severe allergic reaction that can lead to breathing problems and even death.