I just received this information in an email for the Colorado Real Estate Commission:

Crime Alert – Denver police report burglaries of listed homes after holding an open house

The Division of Real Estate has been made aware of criminal activities taking place at open houses listed for sale.   The Denver Police Department has received reports of homes listed for sale being burglarized over the last couple of weeks.  All the homes involved had held an open house and were later burglarized.  Thieves are attending the open house during the day and scouting out ways to gain access; later returning and burglarizing the home. This is an important reminder to take extra precautions with homes you are listing and opening up to the public.  Law enforcement recommends developing a good process for checking and ensuring all access points to the home are secured.  Denver Police are urging everyone to be on the lookout for anything that seems suspicious at homes listed for sale.  If you see suspicious activity or a home that looks like it may have been burglarized, please contact the Denver Police Department through its non-emergency number at (720) 913-2000.