(CBS) — Four children drowned in three separate incidents in the Chicago area over the weekend.

CBS 2’s Marissa Bailey reports the victims included two brothers who drowned in a pit filled with water in Hobart, Ind., Saturday night, prompting their grieving mother to call for more security on the private property where they died.

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Terrion Smith, 8, and Donel Smith, 9, were playing with a group of friends around 7 p.m. Saturday, when some of the friends encouraged the boys to go into a pond that had formed when water filled a pit on property in the 4000 block of Missouri Street.

The boys apparently did not know how to swim. Their friends ran to get help when they realized the brothers were in trouble.

A neighbor tried to rescue the boys, but couldn’t find them.

Neighbors said the property where the boys drowned had been excavated by the property owner. Donel and Terrion’s mother said the area should have been marked and fenced off.

“That’s private property. They should have had it locked off, blocked, or something; gate up there or something. It was nothing over there. Nothing,” Tatiana Smith said.

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Both boys were pronounced dead around 9 p.m. Saturday at St. Mary Medical Center in Hobart.

Two other children also drowned in the Chicago area over the weekend.

A 4-year-old boy drowned Sunday afternoon in the swimming pool of the Royal Fox Country Club in west suburban St. Charles. He was pronounced dead at Delnor Community Hospital in Geneva.

That boy’s name has not yet been released.

Around 4 p.m. Sunday, a 3-year-old girl drowned in a family member’s swimming pool in southwest suburban Morris.

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Her name has not yet been released.