The endangered Iriomote wildcats on Okinawa Prefecture's Iriomote Island face a new threat from an invasion of poisonous marine toads, the Environment Ministry said Monday.

The first such toad was captured on the island in December and since then, seven more have been captured or seen on the island, ministry officials said.

The toads, a very fertile breed about 15 cm long, are native to South America. They were introduced to neighboring Ishigaki Island in the late 1970s in an attempt to exterminate gold beetles, a sugar cane pest, and rapidly proliferated there.