(CNN) -- Three-year-old Casey Lynn Hathaway has been found alive in Craven County, said Shelley Lynch, a spokeswoman for FBI Charlotte field office.
Search and rescue teams from across North Carolina are working in rugged terrain and cold temperatures hoping to find 3-year-old Casey Lynn Hathaway.
More than 100 people, including law enforcement and professional searches, were focusing on up to 1,000 acres of heavily wooded areas on Thursday, Craven County Sheriff Chip Hughes said. Some volunteers had to be turned away because of the difficult conditions search teams are facing.
The FBI, NCIS and dozens of volunteers initially joined the effort to find the boy, described by authorities as 25 pounds and 2 feet 4 inches tall.
Casey was last seen Tuesday. He was playing with two other relatives outside his grandmother's home in Craven County and didn't come inside when the others did, CNN affiliate WTVD reported.
Hughes said authorities are treating Casey's disappearance as a missing child case but have asked the community to report anything "remotely suspicious."
Casey's family searched for 45 minutes before calling 911 on Tuesday, Hughes said.
"We lost my ... grandson," said Casey's great-grandmother on the call, CNN affiliate WCTI reported. "He was walking in the woods back there and we can't find him."
Authorities have employed helicopters, drones and K-9 units, Craven County Emergency Management Director Stanley Kite said. Divers also are assessing nearby ponds, WTVD reported.
The US Marine Corps also has also joined the search effort, Hughes said.
"Today, hundreds of professional searchers and volunteers walked through rough terrain around the home to try and locate Casey," the Craven County Sheriff's Office said Wednesday. "Volunteers were sent home for the night due to safety concerns. Professionally trained searchers will continue to work overnight. Additional search assets will return in the morning."
The sheriff's office has asked residents to check their properties for signs of the missing boy.
"It's heartbreaking. I have two children so I can only imagine what the family is going through and we're a small community so you don't really expect anything bad to happen here," Jonathan Ipock, youth pastor of New Haven Church, told WTVD.