A national group with advanced search technology is assisting in the hunt for a missing Indiana college student last seen over a week ago, police said Sunday.

The private group Texas EquuSearch -- known for its use of sonar equipment and other high-tech capabilities -- is helping in the search for 20-year-old Indiana University student Lauren Spierer.

Spierer, of Greenburgh, N.Y., was last seen by a male acquaintance at around 4:30 a.m. June 3 as she walked to her apartment in downtown Bloomington.

Police said Spierer, who was seen walking alone and barefoot, had spent the night partying with friends.

Bloomington Police Captain Joe Qualters said Sunday that no suspects have so far been identified in the investigation, though he said police continue to receive a steady stream of tips. 

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"We are absolutely undeterred in our investigative efforts to find Lauren," Qualters told reporters Sunday. 

Police announced Friday that 10 people have been identified as "persons of interest" in the case, including Spierer's 21-year-old boyfriend, Jesse Wolff.

Wolff, 21, of Long Island, N.Y., is one 10 people being looked at and is being "cooperative," Bloomington Police Lt. Bill Parker said. Another student, Corey Rossman, reportedly submitted a DNA swab. 

"We’ve not gotten any resistance from anybody at this point," Qualters said.  

The woman's mother, Charlene Spierer, spoke directly to the person or persons responsible for her daughter's disappearance during a news conference Sunday, saying, "I beg you to come forward." 

"To say to the person that has Lauren or that has harmed Lauren, shame on you," Spierer said. 

Addressing her daughter, she said, "I will never leave you ... I love you with all my heart and I need you back." 

Spierer, a 2009 graduate of Edgemont High School in Scarsdale, N.Y., had just completed her sophomore year at Indiana University. She is reportedly studying fashion merchandising and is a University Division scholar.

After an extensive search of the downtown Bloomington area where Spierer disappeared, divers combed Lake Monroe and other area lakes for any clues in the disappearance.

Spierer's father, Robert, said Sunday that the family is offering a $100,000 reward for any information leading to his daughter's whereabouts.

"Anything small could be big," Robert Spierer said. "Speak up and let us help find Lauren." 

SLIDESHOW: Where is Lauren Spierer? 

Click to visit the 'Help Find Lauren Fund'