I've posted about the initial 3 mile ground search and thought I'd post a link to Tucson PD's news release dated April 21.
http://www.scribd.com/fullscreen/90602675
snipped:
The initial responding officers quickly cordoned off the area and conducted another search of the residence as well. As it was evident that Isabel was not in the residence, additional resources were summoned to assist with the investigation of her disappearance and attempts to locate her. The Tucson Police Department called upon the Federal Bureau of Investigation who responded to the area with both Investigative Agent personnel and an Evidence Recovery Team. Additionally, the Tucson Police Department asked for and received assistance from the United States Marshalls Office, who provided a contingent of personnel who participated extensively in the neighborhood search activities. Also, canine handlers with their canine partners, specifically bloodhounds, from the Arizona Department of Corrections were requested and responded to assist.
Search and Rescue personnel from the Pima County Sheriffs Departmentand the multi-agency Rapid Response Team responded at the request of the Tucson Police Department. The Tucson Fire Department assisted with some equipment and personnel needs. The Tucson Police Department also utilized numerous field patrol resources, the Tucson Police Department Air Unit,
various investigative resources (SexOffender Tracking and Registration SORT Unit, Dependent Child Unit, Child Sexual Assault Unit, InternetCrimes Against Children Unit, and Aggravated Assault Unit), as well as
analyst support in order to further the investigation. All potential avenues of investigation have been vigorously explored throughout the day and evening onApril 21, 2012. Search efforts will continue through the evening of April 21, 2012 and into April 22, 2012 as needed.The Tucson Police Department is committed to the mission of finding Isabel and ensuring her safety, utilizing any and all resources that are available."
More pertinent info at link.