Story highlights Police arrest Justin DeRyke, 22, on suspicion of murder

Willow Long disappeared from a rural home over the weekend

Her body was found south of the town of Watson, Illinois

More than 300 volunteers helped search for Willow

A 7-year-old girl who disappeared from a rural Illinois home over the weekend has been found dead, and authorities suspect that a family member killed her.

Police arrested Justin DeRyke, 22, of Watson, Illinois, on Tuesday, according to a statement from the Effingham County's State Attorney's Office.

He is the maternal uncle of 7-year-old Willow Long.

The attorney's office is expected to file charges Wednesday, when DeRyke will make an initial court appearance, the statement said.

Willow's body was found south of the town of Watson.

The girl was watching television with her brothers on Sunday when her mother, who wasn't feeling well, lay down for a nap. When she woke up, Willow had vanished.

When she asked her 3-year-old son where her daughter was, he pointed to the front door.

Willow disappeared between 9 and 10:15 a.m. The second-grader left her glasses at home.

Willow evidently changed clothes before leaving her house. Police said the clothes her mother described her as wearing were found in the family home.

More than 300 volunteers and members of various agencies helped with the search, including the FBI, the Effingham County Sheriff's Office, the Watson Police and the Illinois State Patrol.

No Amber Alert was issued for Willow, as police did not initially suspect foul play.

Search dogs picked up trails around the family property, but there were no other leads.