The foster parents of missing 5-year-old Hasanni Campbell were arrested Friday afternoon in connection with his disappearance, according to Oakland police spokesman Jeff Thomason.

Foster parents Louis Ross and Jennifer Campbell had been the focus of much speculation throughout the investigation into the disappearance of the boy on Aug. 10, KTVU reported.

Police had been mystified as to how Hasanni Campbell could have vanished from a "crowded business district with no witnesses," according to a police search warrant affidavit.

The document supported a warrant to search the home of the boy's foster father, Louis Ross, in Fremont, California.

Oakland police and Crime Stoppers had announced a $10,000 reward in the search for the missing boy, who vanished from the parking lot of the Shuz of Rockridge shoe store in Oakland, California.

Police bloodhounds were unable to detect the scent of the boy outside the upscale shoe store where Hasanni's aunt and foster mother work. His foster father Ross was the last person to see Hasanni alive, a police search warrant affidavit revealed.

Ross said the boy disappeared after he briefly left him outside a car in the rear parking lot of the store. Ross said he went to the store's front entrance to ask Campbell to open the back door, but when he returned to the parking lot, Hasanni was gone.

Hasanni has cerebral palsy and wears braces on his legs.

According to the affidavit, 10 days before the boy vanished, Ross sent an expletive-filled text message to Hasanni's foster mother, threatening to leave the boy alone on a train station platform, the San Francisco Chronicle reported.

Ross said he would look after Hasanni's 1-year-old sister, but not the boy.

"I will watch her but he will be out on the (station) and its your responsibility," said the July 31 text message quoted by police.

In a phone interview Thursday with the San Francisco Chronicle, Ross said he sent the text message in frustration at a time when he planned to break up with Campbell.

"It was me venting about a situation in our past that had come back up," he told the newspaper. "I was ending the relationship at that point."

Besides scouring the area around the shoe store, police have searched Ross' home, the surrounding neighborhoods and parks as well as a scrap yard in nearby Hayward, Calif., that Ross had visited hours before Hasanni's disappearance.

Nothing was taken from Ross' home, and he voluntarily offered his cell phone to police, court records show.

Also Thursday, Ross told television station KPIX that he failed a lie detector test but has cooperated with police "100 percent."

Oakland police would not comment on the court documents or the lie detector test.

Police spokesman Jeff Thomason says Hasanni's disappearance is still a missing person investigation, but says a homicide investigator is in charge of the case.

Click here for more from KTVU.com.

The Associated Press contributed to this report.