Nine people were injured Sunday, two seriously, when they were struck by lightning while swimming at a Chiba Prefecture beach, police said.

All were taken to a nearby hospital after they were hit by the lightening at around 12:30 p.m. at Nakazato beach in Shirako, eastern Chiba Prefecture.

Hitoshi Maruyama, 33, from Kujukuri, Chiba Prefecture, and Yoichi Kikuchi, 32, from Katsushika Ward, Tokyo, were listed in critical condition after their heart and lung operations went into arrest, police officials said. The injuries to the other swimmers were described as minor.

At the time of the incident, it was raining heavily in eastern Chiba and warnings of lightning and heavy fog had been issued, according to the Meteorological Agency.

An estimated 2,500 people were at the beach, but most of them had taken refuge in beach houses and other facilities because of the rain. Lifeguards had urged swimmers to come ashore.