Authorities in Colorado have formally accused two women of murder in the deaths of two young girls whose bodies were found last month.

Nashika Bramble and Madani Ceus, 37, were originally arrested on charges of child abuse causing death, along with two other men and one other woman. Prosecutors added murder charges against them on Friday.

Investigators have not elaborated on what led to the murder charges. An attorney for Ceus who is from Haiti, declined comment on Tuesday. An attorney for Bramble couldn't be immediately reached.

Police have said the girls were between the ages of 5 and 10. Investigators believe they were dead for several weeks before the bodies were located on a farm outside Norwood, about 30 miles west of the ski resort town of Telluride.

"In my 37 years as Sheriff, I have never seen anything as cruel and heartless as this," San Miguel County Sheriff Bill Masters said when the bodies were found.

Authorities have shared few other details about the case that shocked the town of about 500 people. It's not clear how any of the defendants are connected to the children. Authorities haven't released any details about what caused their deaths, and affidavits in the case have been closed to public view.

The others arrested in the case have been identified as Frederick Blair, 23, of Norwood; Ika Eden, a 53-year-old woman from Jamaica and Ashford Archer, a 50-year-old man from Haiti.

Blair and Archer also have been charged with acting as an accessory to a crime.

The Associated Press contributed to this report.