Meanwhile, police in a nearby suburb were investigating Monday whether the disappearance of Jessica Ridgeway is related to two child enticement cases.
Authorities in Arvada didn't find a suspect in the cases from Sept. 9 and Sept. 12 involving a man who tried to lure two boys, around the same age as Jessica, into a car.
Some law enforcement agents with dogs were searching Ridgeway's suburban Denver neighborhood in Westminster, while about 100 others were focusing on an area 6 miles north where the backpack was found.
Jessica was last seen walking to a park where she meets classmates before school.
