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BLOOMINGTON, Ind. -- Police say the boyfriend of a college student from Westchester who vanished at Indiana University was named "a person of interest."

Jesse Wolff, 21, the Long Island beau of missing Lauren Spierer, 20, is one of 10 people being looked at and is being "cooperative," Bloomington Police Lt. Bill Parker said Friday. Another student, Corey Rossman, submitted to a DNA swab, The New York Post reports.

The nearly weeklong search is now being focused on southern Indiana lakes as her family announced a $100,000 reward for information leading to her safe return.

Lt. Parker said divers continued to search Lake Monroe for a second day on Friday to keep up a search he said was sparked by a tip. A search there Wednesday failed to turn up anything related to the disappearance of Lauren Spierer, but Parker said divers hadn't completed their task.

Volunteers, meanwhile, went to Griffy Reservoir on the north side of Bloomington in hopes of finding clues about what happened to Spierer. The petite 20-year-old from Greenburgh, N.Y., was last seen about 4:30 a.m. Friday as she walked alone to her apartment after a night of partying with friends.

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Police say she disappeared after a night out partying with Rossman, whom she took to her place at about 3 a.m. Rossman left with her for his place, sources said.

"We're still needing to pretty much look everywhere," Parker said at a news conference Thursday morning.

Police offered few new details about their investigation. Parker dismissed reports that Spierer had been involved in an altercation in the hours before she disappeared. He said video surveillance and interviews with witnesses showed Spierer had not been involved in any confrontations.

He declined to discuss reports that a male friend she'd been with had been in a fight with other men a couple hours before she disappeared.

Spierer's father, Robert Spierer, urged property owners around Bloomington to check wooded areas, barns and sheds on their property for any signs of her and to call in tips to hotlines police have set up.

"Anything small could be big, so speak up," he said.

The search has sparked an outpouring of volunteers and community support.

John Summerlot, the search operations coordinator for Spierer, said more than 100 volunteers who spent three hours searching along the shoreline and trails at the 100-acre Griffy Reservoir found nothing of apparent importance.

Summerlot, who manages one of IU's residence halls, said one crew descended into a steep ravine and searched areas that were not visible from a road high above looking for clues.

"It's back country hiking down there, really off-road conditions," he said.

Three Indiana graduates who live in Chicago drove to Bloomington to help search.

Malorie Janasek, 25, said she and friends Mackenzie Taylor and Bree Wysocki walked along a causeway at Griffy Reservoir on Thursday afternoon, looking for signs of clothing resembling what Spierer was wearing when she disappeared or anything unusual. They posted updates and photos on Twitter and urged others to join the search.

Janasek, who graduated from IU in 2008, said she lived in the same apartment building Spierer does during her junior year.

"I used to make that same walk all the time. It could have been me, it could have been a friend. It just breaks your heart when you think about it. You feel helpless."

Spierer's father said the family is grateful for the support. In addition to volunteers, local businesses have contributed food, water and other items for those searching.

Indiana University President Michael McRobbie issued a statement of support late Thursday afternoon.

"We will continue to cooperate in every way possible with the Bloomington police and others who are conducting an intensive investigation and search for Lauren," McRobbie said.

"I have met with the parents, as has Provost Karen Hanson, and we both have pledged to them that IU will do all that we can to support them and to help find out what has happened to Lauren... We will continue to assist the family and the authorities in any way that we can."

Dean Foster, the owner of a recently closed coffee shop on the ground floor of Spierer's apartment building, said the outpouring is typical of the college town.

"The community rallies big time," he said. "I think it's probably because it's a really small community that happens to have a big college in the middle of it, and everybody really looks out for each other."

SLIDESHOW: Where is Lauren Spierer?

Click to visit the 'Help Find Lauren Fund'

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