CARLSBAD, N.M. - Crews pulled the body of a 4-year-old boy from a narrow, 30-foot-deep hole in Carlsbad early Monday, nearly two days after he disappeared while playing outside his home next door, state and local authorities said.

Crews reached the boy about 7 a.m. Monday and police spokesman Robert McDonald confirmed the body was Samuel Jones.

He lived in the house next door with his parents and two older siblings, a boy and girl ages 6 and 7, said Carlsbad police spokeswoman Lt. Jennifer Moyers.

"We initially began with rescue procedures and, unfortunately, it was discovered that the conditions inside the hole were not survivable, the amount of oxygen that was there, that type of thing," Carlsbad Police Chief Daniel Fierro told KRQE-TV on Monday.

Some young cousins were at the house Saturday when the boy was last seen playing in the yard.

The rural neighbourhood is a mix of homes and vacant lots. A 4-foot-high chain link fence separates the boy's home from his neighbour's where the hole is located in the backyard. It's possible Samuel could have climbed the fence and simply fallen into the hole, which was dry, Moyers said.

Samuel was reported missing Saturday evening, which prompted authorities to launch a search and issue an Amber Alert.

Family friend Gabriela Morrison told KRQE-TV that moments before he disappeared, Jones' mom said he was playing with toys outside. "She said he may have thrown them over the fence and went over to get them," said Morrison. "She went in for a minute and when she came out, he was gone. She said it was like maybe 25 minutes before she called the police trying to find him herself."

A renewed house-to-house search had just started shortly after daybreak Sunday morning when a detective found the 14-inch-wide hole, Moyers said.

"He wasn't really able to see down in there because it was a fairly deep hole. We began investigating that and did discover that there was a body of a small child," Fierro said.

Efforts to recover the body began Sunday afternoon after a detective shined his flashlight down and saw what appeared to be a boy dressed in clothing Samuel was last wearing. Searchers later sent a camera down the hole and confirmed a child was about 30 feet down in the hole that was around 14 inches in diameter. Temperature and oxygen levels were later taken and showed no signs of life.

The Amber Alert in effect for him was cancelled Sunday night.

A large tracked excavator was used in the recovery along with metal shoring typically used in pipeline construction projects. A specialized search and rescue team from Roswell oversaw the operations.

Carlsbad Assistant Fire Chief Rick Lopez told the Carlsbad Current-Argus that crews also used hand tools and a jackhammer in some areas to break rocks to recover the body.

Authorities are treating the case as a homicide investigation until they can rule on a cause of death.