PHOENIX – The mother of three children found dead Monday night in a Phoenix home admitted killing them and has been arrested, Phoenix police officials said.

The mother, who was not identified, admitted killing her 3-year-old son and two daughters, ages 2 and 7 months, Phoenix police tweeted Tuesday morning.

Police did not say how the children died.

Officials described the mother as a 22-year-old who recently moved to Arizona from Oklahoma.

A call to police Monday night was initially reported as a drowning of three individuals. But the details later changed. Phoenix Fire Capt. Rob McDade later confirmed that three children had died but did not give a cause of death.

Officers who responded to the home had tried to revive the children, who were found unresponsive.

The children's parents and an adult relative were at the home at the time.

Sgt. Mercedes Fortune said the parents had reported the children had been sick earlier in the night.

David Ware, a neighbor, said he initially learned about possible drownings on a neighborhood Facebook page.

"Being that I have kids, I wanted to come out and see if it was a dangerous situation that could jeopardize my children," Ware said.

Ware said police at the scene didn't seem "frantic" and figured the area was secure. He said that the area included a landscaping business, and he often saw trucks coming in and out.

"I've always just assumed it was an active business," Ware said. "I've never seen children on the property."