A 6-year-old boy at a birthday party drowned Saturday at Theodore Wirth Park in Golden Valley.

About 5:30 p.m., someone walking in Wirth Lake noticed a child on the lake bottom in about 4 feet of water, not far from shore, according to the Hennepin County Sheriff's Office.

Lifeguards were alerted, and they pulled the boy from the water and began CPR. The boy was taken by ambulance to North Memorial Medical Center in Robbinsdale, where he was pronounced dead.

The boy, whose name has not yet been released, was from Golden Valley. He was at the park with family for the party, according to the Sheriff's Office.

It's not clear if the boy could swim, said Lt. Chris Mathisen with the Sheriff's Office. "From what we know, he was wearing swimwear and in the water with a group of family members and kids."

It's also not clear how long the boy was under. Two witnesses said it may have been 10 minutes, Mathisen said.

The drowning occurred in a stretch of water patrolled by lifeguards, he said. "The beach was extremely busy and very chaotic with people splashing around and things like that."

Mathisen said the drowning underscores the need for vigilance when kids are in the water. "That's the message we've got to get out there, we need an adult or caregiver to give constant attention. If someone's not watching, it can be over like that."

The boy is the sixth person to drown in Hennepin County this year. Statewide in 2012, the number of drownings has hit a 10-year high, according to state report last week. Prior to Saturday, 25 people had drowned in nonboating incidents.

MIKE HUGHLETT