Experts have confirmed that more than 200 ants found at Aomi Pier on Tokyo Bay on Thursday are highly venomous fire ants.
The red imported fire ants were spotted at a container yard during a survey by Environment Ministry and other officials. The variety is native to South America.
The officials say none of the ants were queens, and no nests have been found. More than 50 queens were spotted at the pier last September and October.
The officials say the newly spotted ants were found about one kilometer from the site where the queens had been sighted last year.
The officials are working to eradicate the ants by placing insecticides around the area. They also plan to investigate the ants' entry route.
Fire ants are active in hot weather. Environment Ministry officials are urging the public not to touch suspicious ants and report any sightings to the authorities.
