Volunteers were walking along railroad tracks and divers wading through ponds on their third day of searching for a missing Virginia boy.
With sticks in hand to comb through tall grass, volunteers tried to remain hopeful.
"Right now most of us believe he still has a good chance of surviving, so we all consider this still rescue oriented," said Martin Dudziak, who volunteered to help search for the boy.
For the second consecutive day, hundreds of volunteers lined up at Kings Dominion to aid the search. Rough terrain is making their work more difficult.
"It's difficult. We're going through briar patches. We walked through a swamp. It's not easy, but it needs to be done," said Laurie Riefmer, another volunteer.
Authorities counted 74 search missions Wednesday, and the efforts will continue around the clock.
"We believe and we are operating under the assumption and with the understanding that Robert Wood Jr. is alive and we are seeking to give him the aid that he need and reunite him with his family," said Capt. Mike Trice of the Hanover County Sheriff's Department.
Robert Wood Jr., 9, wandered away from his family at North Anna Battlefield Park in Doswell, Va. on Sunday afternoon. He hasn't been seen since. Authorities are concerned that he may have wandered away from the 80-acre park.
More than a thousand people spent Tuesday searching a large park. Members of surrounding sheriff's departments, the state police and the National Guard have joined volunteers in the search.
"He's alone, he's afraid," said Battalion Chief Willie Jones of the Hanover County Fire Department. "Children's response sometimes is to hide and that's why we have to be very careful."
Volunteers lined up beginning at 9 a.m. at King's Dominion both Tuesday and Wednesday.
"There's a lot of different animals back there, we've seen bear back there and lot a coyotes," Chris Hutchins of Doswell said Tuesday, returning from an unsuccessful search.
Robert was last seen wearing a red long-sleeved shirt and blue athletic pants. Authorities say that the boy's autism limits his ability to communicate or speak, and that he will not respond to searchers or rescuers. Some searchers also worried about the surroundings.
As night set in Tuesday, members of the search party returned from the woods. Some paused for a candlelight vigil and to pray.
"We're going to try to go out in the morning and start all over," said Kathy Ashworth, who volunteered to help search for the boy.
The family has not made a public appeal for help, but people who know them say they are not giving up hope.
More than a thousand area residents showed up early Tuesday morning to Kings Dominion amusement park, where volunteer searchers were being organized and instructed.
"They told us he's kind of a curious little kid and that he might find something to climb in so we have to make sure we check everything we see," said Peter Billeter, a volunteer searcher.
"I have a child on the autism spectrum and it's a difficult road," said volunteer searcher Courtney Bailey. "This is a hard thing and I feel sorry for the family."