Gwinnett County authorities are working with federal agencies to extradite a Mexican man wanted for the murder of his 4-year-old daughter.

District Attorney Danny Porter said he expects to receive and sign a provisional arrest warrant from the FBI. It will say the county will pay the costs to extradite Mexican citizen Christian Vasquez, 23, from Mexico back to Gwinnett to be tried.

Vasquez is accused of killing 4-year-old Prisi Vasquez. He did so, police believe, with a blow to the head sometime in early 2007, and then fled to Mexico. With him were his wife, Amy Yesemia Ruiz, 20, and her child from a previous marriage. Like Ruiz, the dead child was an American citizen, Porter said.

"We don't have to pay for her extradition costs," he said. "Mexico will just deport her."

Ruiz has been cooperating with the investigation and has told police she is on her way back to Gwinnett from Mexico, Gwinnett Police Public Information Officer Cpl. David Schiralli said.

An arrest warrant charges her with felony cruelty to children for failure to seek adequate medical care for Prisi, Porter said.

"The evidence does not indicate she was there when the violence was inflicted on the child," Porter said.

Gwinnett County Police found the child's body June 20 in the attic of a house on Stillwater Drive in Lawrenceville after a member of the Ruiz family tipped them off.

Friday afternoon, the neighborhood was quiet as most people in the cul-de-sac where the family once lived were away at work. A few doors away, though, Vasquez's sister Judith Vasquez was at home.

Judith Vasquez said her brother is somewhere in southern Mexico. He and Ruiz married about two years ago, she said. She said she had no information about how Prisi died.

Last year, Porter said, Amy Ruiz's family reported to the police that Ruiz and her children were missing. The Gwinnett Police worked the case as a missing person's case. They suspended it after a Ruiz family member told police they had found Amy Ruiz in Mexico.

"Then, last week, a family member told police they had talked with [Ruiz]," Porter said. "She had told them about the death and concealment of the child's body."

The small body was found in a plastic bag in the attic of a rental house on Stillwater Lane. Schiralli said the 4-year-old died of "blunt force trauma to the head."

The current resident of the house said he thought the bad odor he smelled was coming from the garbage disposal or sewer pipes. The child's body had been decomposing for more than a year.

Reporter Eunice J. Lee contributed to this story.