More searchers than ever before — most professional search and rescue teams — were joining the effort Tuesday to find a 12-year-old Boy Scout missing after three nights in the rugged North Carolina mountains.

"This is to show we're definitely still calling this a 'search and rescue,'" Tina White, spokeswoman for the Blue Ridge Parkway National Park Service, told reporters Tuesday morning. "We have no discussions going on whatsoever that are anything other than a search and rescue."

Michael Auberry wandered away from his Boy Scout campsite Saturday evening and hasn't been seen since. Around 35 state and federal rangers went out to search for Michael on Monday but dog teams and a plane with heat-sensing equipment found no new clues overnight.

Michael's father, Kent, told reporters Tuesday that he has the utmost confidence in the officials running the search effort, and that he has no hard feelings toward the Boy Scouts.

"There's no one to blame," Kent Auberry said Tuesday morning, adding that Boy Scout representatives have "been up there day and night searching for him. I know he got the highest level of supervision" on the trip.

Auberry said that before he left for the camping trip, Michael was a little worried that some of his better Boy Scout friends weren't going on the camping trip with him. He wanted $5 from his dad if he didn't have a good time. The father said he'll give him that $5 when he comes home, and the two of them will do something "fun" together.

"We are on a roller coaster, we are up and down and up and down. We have good moments, we have bad moments," Auberry said of how he and his wife are faring emotionally.

"I'm afraid of a lot of things. I'm not afraid that he's wandering around now. I think he's hunkered down" and waiting to be rescued, he added with a quiver in his voice.

White said there was one report that at least one dog showed an "area of interest" in one of the "high probability areas" near the campsite. But nothing else was found to prove Michael was ever at that location.

Officials have been worried about cold weather at night. Overnight temperatures were in the upper 30s to low 40s, milder than on Sunday night, when temperatures dropped into the 20s. There was a chance of rain Tuesday and Wednesday.

"The biggest worry is that it continues another day. We've been worried since the beginning. More time is not good," White said.

Officials Tuesday night separated the search area into 35 different segments. Crews and dogs will focus Tuesday on those different areas, and will shift away from the roads and trails that already have been heavily searched but to no avail.

"We feel that these 35 segments give us the highest probability of success in finding Michael," White said.

No helicopter searches will be conducted Tuesday, however, since areas have been thoroughly covered by air.

"We feel that our best line of action at this point is to put as many people on the ground, heavily, heavily hitting these 35 areas," White said.

The parents, whose son vanished after lunch Saturday with other Scouts and troop leaders, are "very optimistic" their son will be found, White said.

"What we've got here is our son who is lost, lost somewhere out there and we don't know where he is and we've got great professionals out there looking for him and we're just waiting for the news," the boy's father, Kent Auberry, told reporters during the Tuesday press conference.

"We've got a lot of support, we've got a lot of people praying for us, we have friends and family."

"Any sign that he's still out there, that he's still fighting, we're clinging to," Kent Auberry earlier told the News & Record of Greensboro. He and the boy's mother, Debbie Hayes, stayed overnight in a camper at the staging area.

Searchers found Michael's mess kit late Saturday within a mile of the camp site, but no other sign of him has been found, authorities said.

While acknowledging the cold weather, White said Michael was wearing two jackets, one of them fleece. "We've had people who have been out a week or longer and survived," she said.

Hayes told the Winston-Salem Journal that Michael had only potato chips to eat and no water. She also said he takes Ritalin to control attention-deficit disorder. White said searchers have found a candy wrapper and a potato chip bag.

White said Tuesday that Michael only takes Ritalin to help himself focus at school, and that he's not always medicated. He's also gone on many camping trips without his medication, his father said.

"I think it's very important for the family to realize this is not a situation where Michael is a totally different child when he's not on his medication — it's not a Jekyll-and-Hyde type thing," White said. "It's not a concern, with the exception of the fact his parents would like him to have 100 percent behind him when he's going out there."

About 70 people aided by dogs and a helicopter searched the area's logging roads and trails and scoured off-road regions. Searchers planned to stick to the trails at night to avoid losing anyone else.

The FBI was among the agencies on the scene, "but we still do not have any indication of foul play or that this young man has been abducted," White said.

Park rangers worked with the boy's family to learn about Michael's wilderness skills and how he might react to the situation, White said.

Wild animals probably wouldn't threaten the boy, rangers said, adding that weather is the main concern.

A missing persons alert notifying area law enforcement had also been issued as a precaution in case the boy had left the area being searched, White said, noting it was possible the boy could make it to a nearby road.

The boy had stayed behind with an adult leader Saturday morning while the rest of the troop went for a hike "because apparently he wanted to sleep in," said David Bauer, a ranger with the Blue Ridge Parkway. Michael was there when the troop returned for lunch, but the group of about 10 Scouts and their three adult leaders soon noticed he was missing, Bauer said.

Authorities said the boy probably wandered into the woods to explore.

"We're hopeful he was able to find shelter. There are a number of rock crevasses, and he could have covered himself up with leaves," said Mike Lambert, a ranger with North Carolina State Parks.

Bauer said he was not aware of Michael having any arguments or problems with the troop members or his family.

Leaders of other troops drove to the site Monday and offered to help, but authorities asked them to wait because they're not trained in search and rescue.

FOXNews.com's Liza Porteus and The Associated Press contributed to this report.