LIBERTY COUNTY, Texas -

Just before the sun set Friday, a DPS helicopter from Austin circled two-year-old Devon Davis' home. On Saturday, an unmanned drone from Texas Equusearch will take to the skies again searching the 27,000 acres surrounding the home.

"The best benefit of that is unmanned and it can fly for hours," Liberty County Sheriff's Capt. Rex Evans said. "Whereas the aircraft that we've been able to have come over can only stay for a short amount of time."

Volunteers and law enforcement officers ended their search at about sundown Friday. Some carried guns for their protection from alligators and wild boars in the wilderness. The search wrapped up about the time Devon's mother, April Davis, returned home with what appeared to be dinner.

An Amber Alert was issued for Devon Davis on Tuesday. Liberty County sheriff's deputies said Devon wandered off into a wooded area while his mother, April Davis, and 1-year-old sister were napping at their new home in the Sam Houston Lake Estates area near Tarkington at about 3:30 p.m.

Davis said she found the door open and her son was gone. Investigators said Davis told them that Devon opened a latch on the door.

Davis spoke to reporters Friday morning.

"I'm April. I'm Devon's mom. If you know anything, if you've seen anything, please just call somebody. Bring him home with me. He needs to be home with his family. Somebody has to know something, somewhere. Please, help me find my son," April Davis said.

Davis said her son was recently ill and asked that he be taken to a hospital if he's found.

"He's just getting over pneumonia," she said. "He might be sick. Bring him to a hospital."

Davis indicated that she thinks someone has her son.

"If you're scared, I understand there's a lot of stuff going on," she said. "Do the right thing. Bring him to the hospital. Call somebody. People do not vanish. There is something out there and somebody knows something, somebody saw something somewhere. Please find him. Please help me."

Two sources close to the search and investigation told KPRC Local 2 Friday that Davis failed parts of a polygraph test. The sources declined to elaborate on which parts where failed. They stressed that does not mean anything nefarious happened and polygraphs can be imperfect, especially since she is in a very emotional state.

"He is the sweetest child you could ever meet," Davis said of Devon. "He's happy, he's friendly. He's a good kid."

Officials and volunteers have searched by air, land and water, but found nothing. On Thursday, Liberty County officials said the search changed to a recovery mission, meaning that they don't expect to find the boy alive.

Capt. Rex Evans said he had to have a difficult talk with Devon's parents Thursday morning.

"There is a negative end to this that you kind of have to prepare yourself for," said Evans.

Texas EquuSearch has used sonar devices to look for Devon.

"The problem with doing the sonar is there's just so much debris underneath the water," Texas EquuSearch founder Tim Miller said. "You get a false image and you have to go back over it two or three times to determine what it is."

Miller said the terrain is difficult to search because of the woods, water, and wildlife. He said his volunteers have seen alligators, snakes, and wild boars. Immigration and Customs Enforcement agents armed with rifles are standing on the banks while divers search the water to protect them from alligators.

Detectives said they have searched every building in a one-mile radius of the home without luck. The search was widened on Thursday. Dozens of dogs were used to search the area for any signs of the boy.

Investigators have searched Devon's home looking for clues, too.

Investigators said they have not ruled out anything, including the possibility of foul play.

"A third party or foul play is still certainly part of our investigation," Evans said.

Crews said they will continue to search until they find Devon to help give the family closure.

"I need my son," Davis said. "I need to know. I need some answers."

Officials said there is no more need for civilian volunteers. However, water donations are needed because conditions are so harsh.

Devon is 30 inches tall and weighs 40 pounds with red hair and blue eyes. He was last seen wearing a red and gray jersey T-shirt, jeans and Spiderman tennis shoes.

The Davis family has only lived in their home a week. They moved to the area from Virginia.

Anyone with information regarding Devon's whereabouts is asked to call the Liberty County Sheriff's Office at 936-336-4500.