Helping to organize the searchers looking for missing pregnant mother Jessie Davis Thursday is Texas EquuSearch Mounted Search and Recovery Team, a Dickinson, Texas-based group that travels the country aiding the hunt for lost persons.

Davis, a 26-year-old pregnant mother from North Canton, Ohio, was last heard from on June 13. Her 2-year-old boy was found home alone on Friday and told authorities "Mommy broke the table. ... Mommy's in the rug."

The nonprofit organization was formed in 2000 as a mounted search-and-rescue team made up mostly of volunteer horse owners in the North Galveston County area.

"We do all the legwork," the group's director, Tim Miller, told FOX News. Police, he said are "just overwhelmed with leads and stuff to come in, and they've got to follow every single lead ... It's impossible for law enforcement to do the actual search and investigation, too."

With more than 350 members, the group's primary focus is horse-mounted searches, but it is equipped to scour areas by air and water as well — giving law enforcement an added hand to follow up on leads.

"We're just a resource for them," Miller said. "They call us with leads and say, 'Hey, we got a lead here. Can you get searches out to this area?' It frees them up to do their job."

The group has participated in hundreds of searches and has recovered the bodies of 21 missing people, helping law enforcement comb through rural areas.

"We determine how large the [search] area is and then how many people we need in that area to go ahead and cover every square inch," Miller said.

Much of the time, Miller said, the searchers focus on rural areas.

"We know that the majority of the time that when somebody does something, they do find a rural area," Miller said. "They do a quick dump and get out of there."

The nearly 1,000 volunteers who turned out Thursday to help search for Davis will be advised to look for anything out of the ordinary.

"We're telling our searchers that they need to look for anything that's out of place, any tire tracks that go into something, any building materials or debris that looks like its been dumped," Miller said. "We're going to be looking underneath everything."

And in the Davis case, as with all missing persons searches, time is of the essence.

"If she is not alive, the sooner that her body is found, they can determine cause of death," Miller said. "Hopefully some evidence is around there that will help the case."

Miller's own daughter, 16-year-old Laura, was abducted and murdered in 1984. He founded Texas EquuSearch in her memory.