A national missing persons search group is joining the hunt for a 22-year-old Ohio woman last seen more than two weeks ago.

Texas-based EquuSearch will be in Ohio Tuesday to search for Katelyn Markham, who was last seen Aug. 14 at her home in Fairfield, near Cincinnati, Fox 19 reports. 

Dozens of volunteers, including friends and family, have so far assisted police in the search for Markham, who was reported missing by her fiance, John Carter. Searchers looked in Fairfield's parks over the weekend and have posted a $5,000 reward for information that leads to finding her. 

A picture of Markham has also been displayed on an electronic billboard in northern Kentucky, urging motorists to contact police with any tips about the 22-year-old Ohio woman. 

Markham's father, meanwhile, has issued a public plea for his daughter's safe return.

Dave Markham spoke on NBC's "Today" show Monday morning, expressing hope that somebody knows something that can help find his daughter. 

Carter reportedly said he last saw Markham the night of Aug. 13 when the two were discussing a possible move to Colorado. 

"I know you're not supposed to report a missing person before 24 hours, but my fiancee is missing and I can't find her anywhere," Carter said. 

"We were planning on going in October and then we pushed back the date to November," he said. "We could have pushed the date back a year and it would not have mattered. I didn't want to make her do anything she didn't want to do, and she did not feel like she was being forced into anything."

When asked what he meant by "forced," Carter said, "Just going to Colorado, the marriage, the whole thing. It was entirely up to her."

Carter told police that there was a festival "going on right up the street" with "a lot of questionable people there."

In an interview with Fox 19, he elaborated on the comment, saying, "I don't think it draws shady, sketchy people, but there were so many people there you don't know everybody's intentions there."

Police have said they have no evidence of foul play but can't rule it out.

Markham is described as 5 feet, 3 inches weighing 130 lbs. She has green eyes and brown hair with blond highlights. Anyone with information on her whereabouts is being urged to call CrimeStoppers at 513-352-3040 or Fairfield police at 513-829-8201.

The Associated Press contributed to this report 

Click here for more on the disappearance of Katelyn Markham from Fox 19