LAS VEGAS (AP) — Police in Las Vegas have opened an internal investigation into why it took authorities 17 hours to find two children who were left for dead.

The girl was found dead and her brother severely injured at an extended-stay hotel south of the Las Vegas Strip Monday morning, hours after their critically injured parents were found at a different hotel. Police on Wednesday said the internal review is meant to identify what the department could have done better.

Police have accused convicted felon Marcus Maddox of severely beating the mother of their two children before shooting himself in the head while on the phone with a dispatcher. Detectives believe Maddox killed the girl and injured the boy before attacking their mother.

The boy, Maddox and his estranged wife remain hospitalized in critical condition.

The Las Vegas Review-Journal reported that police made several calls to the Clark County Department of Family Services Sunday night, but they were not returned until Monday morning.

Police Lt. Dan McGrath on Wednesday told the Las Vegas Sun that the department had addresses linked to the case, but none were for the site where the children were found. The newspaper reported that a case worker with the county’s Child Protective Services first found the children after responding to an alert from police Monday morning.

The Department of Family Services has a 24-hour hotline for law enforcement that is used to reach the agency’s staff after hours. County spokesman Dan Kulin in a statement said officials “are reviewing the information we have and will be sharing that with Metro to better understand what transpired and determine whether any policies and procedures need to be changed or reinforced.”

Police spokesman officer Jacinto River said the department currently believes that Child Protective Services acted appropriately.

Records showed Maddox facing multiple felony charges, including attempted murder. They did not list his attorney.

Maddox, 30, served time in Nevada state prison for convictions in 2005 on attempted murder, burglary and weapon charges, according to Nevada Department of Corrections records.