Aggressive red fire ants have been found in a container yard at Kobe port in western Japan after being discovered for the first time in a container that arrived at the port last month, the Environment Ministry said Sunday.

About 100 fire ants have been found in the port, the ministry said. The Kobe municipal government said there is no need for concern as the nearest residential area is located 2 kilometers away from the container yard.

(Environment Ministry)

Red fire ants, ranging in length from 2.5 to 6 millimeters, originated in South America and are known to be aggressive. People can develop anaphylaxis when stung.

The container arrived at the port on May 20 from Guangzhou, China, and was stored there until May 25, the ministry said.

Fire ants were found when the container was unloaded the next day in the city of Amagasaki in Hyogo Prefecture and were exterminated.

The ministry searched the container yard Friday and found fire ants in an asphalt crack.

"As those found were worker ants, it is unlikely that an ant colony has been created with the presence of a queen," a Kobe municipal official said.

The ministry has spread pesticide in surrounding areas and is searching for other fire ants.