Investigators in Westminster said they would bring in an aerial search team and tracking canine units to augment the massive police and volunteer search parties combing the area to find Jessica Ridgeway.
The girl was last seen by her mother walking three blocks to school Friday. She never arrived at the park where she normally met friends to complete the walk to school, The Denver Post reported.
Police found the girl's backpack and water bottle Sunday about 6 miles from where she had last been seen.
Police have searched area waterways using divers equipped with sonar.
Investigators also started a push on social media and released two more photos and a video provided by the family. Two vigils were scheduled Tuesday to pray for the girl's safe return.
Jessica's mother, Sarah, works overnight and was asleep when her daughter left for school. She also did not get the message initially when the school called to tell her Jessica was absent -- so the initial call to police was delayed.
Police say Jessica's father is engaged in a custody battle with her mother. He lives out of state and police said they do not believe Jessica is with him.
The FBI is examining the possibility a sexual assault on an 11-year-old Cody, Wyo., girl may be linked to Jessica's disappearance, ABC News reported Tuesday. Cody is about 500 miles northwest of Westminster.