Smithfield — Search and rescue teams from at least four departments set out Monday afternoon on the ground and in the air as authorities continued their search for a 3-year-old boy who went missing Sunday morning from a local flea market.

Captain David Daughtry, a member of the Johnston County Sheriff's Office Search and Rescue team, said officers have extended the radius of their search up to one and a half miles from Brightleaf Flea Market on U.S. 301. Daughtry said authorities had already checked the building's interior and surrounding fields and thickets twice since Siraj Munir Davenport disappeared.

Daughtry said the Sheriff's Office also dispatched a boat Monday morning to scour the Neuse River, which runs along the edge of the property. But after a search of a 4-mile stretch of the river turned up nothing, rescue teams decided to focus their efforts on the ground, he said.

Volunteers from the Arrington Volunteer Fire Department in Wayne County joined the search efforts on Monday, scouring a wooded area northeast of the flea market on ATVs. The state Highway Patrol assisted from the air, but Daughtry said fly-overs hadn't resulted in any leads on Davenport's whereabouts.

Meanwhile, as more time passes, authorities are worried that Davenport's life might be at greater risk if he remains outdoors. "There are any number of scenarios that could be in play as far as his safety goes," Daughtry said.

Smithfield Police Chief Steve Gillikin said that officers haven't found evidence suggesting that Davenport was kidnapped when he disappeared from his mother's side Sunday morning. But Gillikin didn't rule out the possibility.

"We're approaching it from the perspectives of both a missing person case and a possible abduction," he said.

An Amber Alert remains in effect for Davenport, of Four Oaks, who police say wandered from his mother's side late Sunday morning as she loaded the family car. Sgt. R.L. Capps, the lead investigator in the case, said Sunday that the boy's mother waited about an hour before calling authorities. He said the mother and her friends tried to find the boy first.

Siraj Davenport, who also answers to "Raji," is about 3 feet tall and weighs 35 pounds. He has dark brown hair and brown eyes. He was last seen wearing a light-blue shirt imprinted with a yellow truck, dark blue sweatpants and blue Adidas tennis shoes.

Police have set up special tip lines for anyone who might have information on Davenport's whereabouts. Tipsters can call 989-5729 or 989-5740.