Rachel Henry, 22, told investigators that she suffocated her son and two daughters with her hands, according to police, but she pleaded "not guilty" in court Tuesday in Phoenix.

NBC News reported that she made no other comments apart from confirming her identity.

Henry is charged with first-degree murder for the deaths of her children: 3-year-old Zane Henry, 1-year-old Miraya Henry and 7-month-old Catalaya Rios. The children were killed Jan. 20.

A makeshift memorial grows in front of the home where Rachel Henry was charged with killing her three children. The children were found dead inside the family home  in Phoenix. 

Credit: Ross D. Franklin

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Credit: Ross D. Franklin

After allegedly smothering the three children to death, “Rachel placed all of the children in a position on the living room couch as if they were napping,” according to a police report. There is no reported motive.

Henry has a history of methamphetamine addiction but wasn’t under the influence of drugs at the time of the killings, according to The Associated Press.

"Everybody is in shock. Like how do you do that to your babies? Like something had to not have been right." — Sherri Underwood to 12News

Henry is being held on a $3 million bail. Her trial will move forward March 24 with an initial pretrial conference.

»MORE: Report: Mother smothered each of her 3 kids to death, while singing to them