A nine-year-old Wisconsin boy died from a lightning strike, one of eight boaters who sought shelter on a Lake Superior beach, Minnesota authorities said.

Luke Voigt, 9, of Iron River, Wis., was one of eight family members and friends who were on a sailboat that took refuge about 5:30 p.m. Saturday from a rapidly approaching thunderstorm near the Duluth-Superior harbour, the St. Louis County Sheriff's Office said Sunday in a news release. Lightning struck before most could get off the boat, but one person was able to call 911.

Law enforcement and rescue agencies rushed by boat and ATV to the site on the end of Minnesota Point, near the Superior Entry to the Duluth-Superior harbour, about three kilometres from the nearest road to Duluth, Minn.

Luke was flown to a hospital in Duluth, where he was pronounced dead. Four others were taken to Duluth hospitals with what authorities described as severe but not life-threatening injuries.

The sheriff's office said the others aboard the boat included Paul Voigt, 46, Laurie Voigt, 45, and Daniel Voigt, 7, all from Iron River, Wis.; John Lintula, 52, and Vicky Lintula, 50, who are both from Wisconsin but their hometowns weren't listed; and Frank Voigt, 79, and Mary Voigt, 78, both of Pierz, Minn. The release did not say which survivors were seriously injured.

While authorities initially said Saturday that everyone had been injured, the sheriff's office later said the seven-year-old was on shore when the lightning struck and was not hurt.

Assistant Fire Chief Jarry Keppers told the Duluth News Tribune the nine-year-old boy was found face-down in the water by his brother, who turned him over. He said the other passengers on the 26-foot sailboat started CPR, which was continued by rescue workers who got a pulse back.

Because of the difficulty in getting to the site, Keppers said, about 25 minutes elapsed before the first firefighters arrived by boat.

"It's one of the more remote areas of the city," Keppers said.

Except for the nine-year-old, all were taken by boat to Sky Harbor Airport or the Duluth Coast Guard Station, both of which are on Minnesota Point, a sand spit also known as Park Point that juts about 11 kilometres into Lake Superior from downtown Duluth. From there, they were driven in ambulances to hospitals, Keppers said.