The Westminster Police Department tweeted a message asking people to stay out of the area while they brought in tracking dogs to follow the lead.
The last reported sighting of Ridgeway was Friday morning when she left to walk three blocks from her Westminster, Colo., home to meet friends for the walk to school. According to ABC News, it was a route she took every day, but this time she never got there.
The discovery of the backpack and water bottle on Sunday came after an army of eight hundred volunteers scoured trails and hillsides near Jessica's home on Saturday.
"Right now they're just asking us to find anything that's out of the ordinary, any kind of evidence we could find," volunteer Monty Yanker told reporters.
While an Amber Alert was issued Friday night for the 10-year-old, nearly eight hours after she disappeared, police officers and FBI agents set up road blocks to ask drivers if they had seen or heard anything out of the ordinary.
Reports indicate that school officials called Ridgeways home after they realized that she hadn’t shown up for class.
But Jessica's mother, who works the overnight shift at a tech company, was asleep and didn't get the message, which delayed her calling police.
"When we start with an eight-hour delay, or a delay as substantial as this, the distance that she could have wandered even on her own just gets huge," Westminster Police Detective Trevor Materasso told reporters.
Police say that Jessica's father, who lives out of state, is in a custody battle with Jessica's mother, but do not believe she is with him.
"We don't have a person of interest. And we are going to look at every angle multiple times," Materasso said.
Jessica was last seen wearing blue jeans, black boots, a black puffy jacket, and pink and purple glasses, ABC affilate KMGH-TV in Denver reported.