(CNN) -- Police are asking that the volunteer searches for three missing Michigan brothers be stopped by Friday night.
Local authorities and federal investigators have been trying to find 9-year-old Andrew Skelton, 7-year-old Alexander William Skelton and 5-year-old Tanner Skelton last seen on Thanksgiving.
The end of the volunteer searches will allow authorities the opportunity to process what has been done and collected and to "re-evaluate our direction for the following week," said Larry Weeks, police chief of Morenci, Michigan.
John Skelton, the boys' father who has been charged with parental kidnapping, is fighting his extradition from Ohio, authorities said Wednesday. A hearing is set for December 14.
Skelton was arrested Tuesday upon his release from a mental health facility where he was being treated after a suicide attempt, Weeks said.
Although investigators have found "a number of items," they still do not know the children's whereabouts, Weeks said.
Asked whether he believes that the boys are dead, Weeks said Wednesday, "I refuse to believe that at this point," saying he wanted to maintain hope. He did, however, repeat his Tuesday statement that a positive outcome is not anticipated.
Investigators have not spoken with Skelton "in some time," he said, or developed any additional information. He previously said authorities are skeptical of the information Skelton has provided.
Skelton said he left the three boys with a woman, whom he identified as Joann Taylor, the morning before he tried to take his own life -- in part to ensure that they did not witness his suicide attempt.
Skelton said Taylor was supposed to take the boys to their home in Morenci, a southern Michigan town of about 2,400 people about 40 miles west-northwest of Toledo, Ohio, Friday afternoon, Weeks said. But the boys never arrived.
Earlier, authorities determined that Skelton had no "established relationship" with the person he named as Taylor, and they aren't certain that she even exists.
Authorities continue to ask for the public's help, hoping someone saw Skelton's blue 2000 Dodge Caravan, in which he was believed to be carrying the boys along a 25-mile stretch of road between Morenci and Holiday City, Ohio.
The last time someone other than a family member saw the boys was at 5 p.m. on November 25, according to the chief.
Police say Tanner is 3 feet, 6 inches tall with strawberry blond hair and blue eyes, and weighs about 40 pounds. Alexander is 3 feet, 9 inches tall, has brown hair and eyes, weighs about 45 pounds and has scars on his hairline and chin. The oldest brother, Andrew, is 4 feet, 1 inch tall, has brown hair and eyes and weighs roughly 57 pounds.