Small Ohio Town Is Focus of FBI Probe After Strange Deaths and Disappearances The relatives of the dead and missing women think the cases are connected.

 -- The FBI is now helping to investigate a string of disappearances and murders that have taken place in a small Ohio town over the past 13 months.

Six women have vanished in the town of Chillicothe since May of last year and four of those have been found dead, authorities said. The women who disappeared were mostly in their 20s and 30s and were mothers. One victim was a grandmother with her third grandchild on the way, authorities said.

Lt. Mike Preston of the Ross County Sheriff’s Office would not say that he believes this is the work of a sole serial killer, but that is the theory supported by many of the relatives of the women.

"We've got too many women missing in our community and it's time to get some answers," Sheriff George Lavender said at a press briefing on Monday.

Tameka Lynch, a 30-year-old married mother of three, was the second woman to go missing in the area when she vanished in mid-May, 2014.

“I felt that after the first three women went missing a year ago, it had to be someone they all know and trust to even go with them, and it has to be more than one person -- my daughter was not a small person,” Angela Robinson, Lynch's mother, told ABC News.

Most of the six women had a known history of drug use, with at least three having had an addiction to heroin, family members told ABC News. Friends have reported that some of the women were known prostitutes, and while some relatives were unable to confirm that their daughters and nieces were involved in prostitution, Robinson said she thinks that the association kept police from doing more earlier.

“I don’t think they were worried because they were just saying ‘these are just women who are strung out on drugs, or doing whatever,’” Robinson said.

Charlotte Trego

The first to disappear was Charlotte Trego, and she has not been seen since, authorities said.

“I last spoke with Charlotte on May 3, 2014,” her mother Yvonne Boggs told ABC News, “and she told me, 'Mom, I’m ready to come home and get clean.'"

Tameka Lynch

Lynch disappeared the same day as Trego, and it has since been revealed that the two women knew each other. Unlike Trego, however, Lynch’s body was found three weeks later on May 24 in Paint Creek, which runs just outside Chillicothe.

Robinson said that police have told her that it was clear Lynch had died before being put in the water, which Robinson said proves her death was not an accident.

“She was scared to death of water. She wouldn’t go swimming, and she was scared of the woods,” Robinson said.

“She would do anything for anybody. ... That was her biggest downfall,” she said of her daughter.

Wanda Lemons

There was a six-month break in the disappearances until Wanda Lemons, 37, disappeared late last year.

“She called me in November, the 1st of November, and we were talking about Thanksgiving dinner and spending some time with me,” her mother Diana Willett told ABC News.

Lemons, who has not been seen or heard from since, has five children ranging in age from their early 20s to her youngest, 6-year-old Heaven. She also has two grandchildren with her third on the way.

Willett said that her daughter was "using drugs," including heroin, around the time of her death and while she “couldn’t say for sure” if her daughter was working as a prostitute, “I’m not going to deny she wasn’t, because she had before.”

Shasta Himelrick

Shasta Himelrick was the fourth woman to vanish, on Christmas Day, 2014. The Chillicothe Gazette reported that the 20-year-old was pregnant and her body was found in a nearby river on Jan. 2.

Non-fatal levels of oxycodone and cocaine were found in her system at the time of her death, the newspaper reported, and the coroner ruled it a suicide because her body showed "no sign of pre-mortem trauma."

Tiffany Sayre

Tiffany Sayre was the most recent disappearance when she went missing on May 11. The search lasted more than a month for the mother of two toddlers, and her body was found wrapped in a sheet in a wooded area on June 20, Father’s Day.

“Makes me mad, makes me hurt," her father Thomas Kuhn told ABC affiliate WSYX. "All I know is we are going to catch you, whoever you are, we are coming for you.”

Police have not publicly specified what cases they are looking into and refused to say officially that they are connected, but Preston, of the Ross County Sheriff’s Office, told ABC News that they are looking at six cases.

The Chillicothe Gazette reported that investigators were also looking to see if the shooting death of Timberly Claytor was connected to the other cases, even though police have announced a suspect in that case.

The FBI is now involved in the case and the relatives, many of whom have begun meeting on a weekly basis to discuss the case, said they are happy to have the extra help.

“It’s awesome,” Willett said of the FBI’s involvement. “[They] should’ve done it a long time ago when all this started happening but they're doing their job now.”

ABC News' Ali Ehrlich and Alex Perez contributed to this report.