Police in Arizona said an officer called child protective services in January with concerns about a mother who was arrested Tuesday and accused of killing her two young children.

>> Read more trending news

Officers were called to 21-year-old Brittany Velasquez’s home in Superior more than a half-dozen times before her arrest on two counts of first-degree murder, interim Superior police Chief Christian Ensley said.

“We’re still looking at our records,” he said Tuesday at a news conference. “We know at least one incident that happened on Jan. 3, where CPS was contacted in reference to the children. I don’t know what action, if any, CPS has taken.”

Ensley said one of his officers called because he feared for the safety of Velasquez’s children after responding to a report of a theft at her home in January. Officers determined that the incident wasn’t a theft, but became concerned after speaking with Velasquez’s relatives.

“It was reported by a relative that she would often leave her kids at the home and expect someone else to care for them,” Ensley said.

The Arizona Department of Child Safety confirmed to AZFamily.com that the agency opened at least two investigations into possible neglect involving Velasquez and her children. The first case was opened in October 2016 and the second in January 2018.

Officials told AZFamily.com that the cases were closed because officials "said they never found evidence of neglect or a dangerous environment for the kids."

Police said Velasquez lived in Superior with members of her extended family. The father of her children, whose name was not released, died last year.

Officials didn't identify the children, although family members named them as 10-month-old Brooklyn and 2-year-old Christopher in a GoFundMe campaign launched to raise money for their funerals.

"They were so innocent," Brittany Valesquez's sister, Amber Velasquez, told AZFamily.com. She said she's still reeling from the loss of not just her niece and nephew but also of her sister.

“We would talk every day, all day. I know what she did was the most horrible thing, but at the same time that was my sister,” she said. “Anyone who would commit that crime, I would want them to be arrested and face their punishments for what they did.”

Authorities declined to share the circumstances that led to Brittany Velasquez’s arrest, saying only that investigators found evidence of foul play. Ensley said officers were called by Brittany Velasquez just before 11 p.m. Monday after she unsuccessfully attempted to revive the children with CPR. They had been found dead in a vehicle while still strapped into their car seats, according to officials.

Pinal County Sheriff Mark Lamb said Tuesday that authorities were awaiting the results of autopsies and toxicology tests for the children.

Superior is located about 60 miles east of Phoenix. Its population was measured at about 2,800 people during the 2010 U.S. Census.

“This is a small community. Most of us know each other,” Ensley said. “This kind of thing doesn’t happen around here. This is a massive blow. … It has absolutely rocked Superior.”