Authorities arrested a man in the death of his 19-year-old girlfriend, whose younger sister died mysteriously six days later, authorities said.

Prosecutors were investigating whether the second death was a homicide.

James McFarland Jr., 23, who was the father of his girlfriend's infant daughter, was being held without bond Wednesday at the Wayne County Jail. He was arrested without incident Tuesday at a friend's home, police said.

Authorities said McFarland faced a preliminary murder charge for the death of Erin Stanley, whose body was found Sept. 1 at her parents' home in Centerville, just west of Richmond. Her 18-year-old sister, Kelly, was found dead in the home on Sept. 7.

A pathologist's analysis of autopsy evidence showed that Erin Stanley was strangled, Wayne County Prosecutor Mike Shipman said.

Kelly Stanley's death has been termed "suspicious" as investigators await the findings of a pathologist's report. Shipman said he would not now name a suspect in Kelly Stanley's death.

McFarland was the father of Erin Stanley's infant daughter and lived with the Stanleys. He denied any involvement in either woman's death. In an interview last week with the Palladium-Item, he said he planned to marry Erin and was devastated by her death.

"I've got nothing to hide," he told the newspaper. "I didn't have anything to do with either death."

Shipman said Wednesday he planned to file formal charges by the end of Thursday, after which an initial court appearance for McFarland could be scheduled. Shipman said he did not know whether McFarland had a defense attorney.

Officials had released little information about the deaths in the town along U.S. 40 about 60 miles east of Indianapolis.

The sisters' mother told a 911 dispatcher that Erin was found unresponsive and laboring to breathe by her boyfriend, according to a recording of the call made at 5:15 a.m. Sept. 1.

Centerville Police Sgt. Ed Buchholz said that in the days leading to McFarland's arrest, he interviewed McFarland once and a second interview was halted when McFarland invoked his right to an attorney.

"He has been a person of interest from the start," Buchholz said.