A man has confessed to the killings of an Arizona couple missing for a week.

Michael and Tina Careccia vanished on 22 June after leaving their home to go to work, but never arrived. Their 2008 Honda Accord was discovered abandoned about half a mile from their home in Maricopa, about 35 miles south of Phoenix.

Police have detained Jose Valenzuela, 38, who resides at the Maricopa property where the remains were found. He was found in the possession of a .22 calibre revolver that authorities believe is the murder weapon.

The arrest comes a day after a search warrant was served at the house, not far from where the Maricopa couple's vehicle was found.

Pinal County Sheriff Paul Babeu said Jose Valenzuela, 38, acknowledged killing Michael Careccia, 44, and his wife, Tina, 42.

"Essentially he confessed," Babeu said at a news conference.

Valenzuela told investigators he and the couple have been acquainted for the past two years and used methamphetamine together. Authorities said Valenzuela brought meth to the couple's home the day before they went missing on Father's Day. Then they went to Valenzuela's home later that day and an altercation occurred.

Babeu said authorities believe Valenzuela was high on meth at the time of the killings.

His statements to an investigator led to a search for the victims on his property. Babeu said Valenzuela borrowed a backhoe from an unsuspecting acquaintance to hide the bodies on his property in Maricopa. The grave was not noticeable initially because the suspect had piled other debris and materials on top of it, Babeu added.

"Instead what he did was he built, not a makeshift grave, but an actual 6-foot grave," Babeu said. "He put these victims in that grave and buried them."

Video footage had shown investigators digging in an area close to the home on Wednesday night. Volunteers in jeeps, quad bikes, dirt bikes and trucks joined police officers during several days of searches in a remote area outside Maricopa.

Geoff Dugan, Mr Careccia's brother-in-law, said: "We knew there was foul play from the get-go. There's no reason they wouldn't come home."

Valenzuela has been charged with two counts of first-degree murder. He is being held on a $2 million cash bond.