TAIPEI (Taiwan News) — More than 300 venomous fire ants have been found in shipping containers traveling from China to Japan's Yokohoma Port.

Local authorities in Japan said they are working with the Ministry of Environment to determine the origin of the imported insects. According to NHK, the containers from Chinese freighters entered Yokohoma Port at the end of last month and were transported to a business operator in the central Japanese city of Odawara.

After security checks, the officials discovered fire ants inside the containers, including approximately 20 giant, fertile ant queens with wings.

The Yokohoma city government confirmed that it was the first time a fire ant queen had been spotted in the city. It stressed it is conducting an investigation to see if the ants have spread to surrounding areas and promised it will exterminate the unwanted stinging insects any way it can.

The government also warned Japanese citizens to avoid trampling on fire ants or breaking their nests since they are highly toxic and aggressive.

According to Liberty Times, fire ants, or more specifically red imported fire ants (Solenopsis invicta), are native to South America and were first spotted in Japan in 2017. Once bitten, most victims experience intense burning and swelling on their skin, followed by blistering that is potentially fatal.