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USA TODAY

DETROIT - A 22-year-old Detroit man has been charged withsexually assaulting, killing and burning his girlfriend's 5-year-old daughter in July 2011, according to the Wayne County Prosecutor's Office.

Mariha Smith was last seen sleeping in the front room of her house at 3:30 a.m. July 24, 2011, according to investigators. Her 26-year-old mother reported her missing a few hours later.

Darnell Cheatham is expected to be arraigned Monday on charges of first-degree, premeditated murder, arson, torture, child abuse and dismemberment and mutilation of a body, Wayne County Prosecutor Kym Worthy said.

"This very difficult case was solved due to the diligence and tenacity of Wayne County prosecutors and Wayne County Prosecutor's Office investigators," Worthy said in a press release. "Much of the work was done on their own time to finally bring justice to little Mariha."

The Detroit Fire Department was called to a fire in an abandoned home at 8 a.m. that day. After the fire was extinguished, they found Mariha's charred body on top of a mattress.

Investigators say Cheatham spent the early morning hours of July 24 with her mother, left the house with Mariha, sexually assaulted and killed her, then set the mattress on fire in the home about a dozen blocks away.

Cheatham, who was dating one of Mariha's aunts, is expected to be arraigned at 2:30 p.m. Monday in 36th District Court, court officials said. Preliminary examinations for felony cases happen in this Detroit court.