The search for a missing 7-year-old boy suspected of running away from home entered its fourth day Tuesday after police and hundreds of volunteers failed to find him over the holiday weekend.

Authorities believe Ricky Holland (search) voluntarily left his house in Williamston, about 15 miles east of Lansing in Ingham County (search), after his parents put him to bed on Friday night. He was reported missing Saturday.

The Ingham County Sheriff's Department said Tuesday that authorities continued their search for the boy. After failed searches Saturday and Sunday, about 50 police officers joined volunteers in the search on Independence Day.

Ricky's parents, Tim and Lisa Holland, said the ordeal is taking a toll.

"Right now I feel numb," Tim Holland told the Lansing State Journal. "I feel like I have nothing left to give. All I have left is hope and prayer."

The Hollands discovered that Ricky was not sleeping in his bed Saturday morning, and a statewide Amber Alert (search), where broadcast media outlets are asked to air information about a missing child, was later issued.

The Hollands found Ricky's bed pushed toward an open window, and his backpack and shoes were gone. The boy has run away before, but never for this long. The Hollands asked anyone who has seen Ricky to call the sheriff's department.