The young man believed to be the last person to have seen Lauren Spierer prior to her disappearance denied that allegation moments after giving Bloomington police a DNA sample Friday.

"I was not the last person with her. That's all I can say," Rossman said.

Investigators said Rossman was with Spierer until they got to his apartment building at 11th and Morton.  One of their friends told police he watched Lauren leave the building on foot and make it to 11th and College Avenue.  It's the last place anyone says they saw Lauren but police cast doubt on that story.

"The last place that we can be totally confident she was is further south. Again, we're just going on various statements to place her at the more northern part," Lt. Bill Parker said.

Police said the last place video cameras saw Lauren was just behind Crossman's building in an alley a little after 3:00 a.m. last Friday. Officers found items there believed to belong to Lauren.

"We found keys and the small card purse or coin purse in the alley," Parker said.

Police are focusing on a total of 10 persons of interest. They are people who saw Lauren in the hours before her disappearance.  Investigators said they haven't been able to talk to all of them. Fox59 has learned that police do plan to polygraph test some, if not all of them.

All this as Lauren's family keeps begging for help and information.

"Anything small can be big. If you have any information about Lauren or the events of that night speak up and help us find her," Robert Spierer said.

The volunteer effort to find Lauren has been described as impressive. Her family is offering a $100,000 reward for information that breaks the case.

Attorney Ken Nunn is also offering a $25,000 reward for information leading to the capture and conviction of any persons responsible for her disappearance. Indianapolis Colts owner Jim Irsay also tweeted that he is offering a $10,000 reward for serious information that solves the case.

Lauren Spierer is described as approximately 4' 11" with a slender build. She has blue eyes and blonde hair, longer than shoulder length. The 20-year-old had just finished her sophomore year at IU. Her mother, Charlene Spierer, said her daughter has a life-threatening heart condition called Long QT Syndrome. If anyone knows where Lauren is, they are asked to please take her to a hospital.