06/09/2011 09:30 am ET Updated Aug 09, 2011

Corey Rossman, Last Man To See Missing IU Student Lauren Spierer Blacked Out After Alleged Dorm Altercation

BLOOMINGTON, Ind. (AP) -- Bloomington police say a missing Indiana University student wasn't involved in any altercations before she disappeared.

But Lt. Bill Parker won't discuss reports that a male friend with 20-year-old Lauren Spierer (SPEER'-ur) was in a fight with other men a couple hours earlier.

Parker said divers would return to nearby Lake Monroe after a search Wednesday turned up nothing. Hundreds of volunteers have joined in searches for the Greenburgh, N.Y., woman since she was last seen about 4:30 a.m. Friday walking alone to her apartment after a night of partying.

Her father, Robert Spierer, says a $100,000 reward is being offered for information leading to her return. He asked Thursday that people living around Bloomington check wooded areas, barns or sheds on their property for any signs of her.

After reviewing security tapes in the building, police say that "a male friend" was seen entering and leaving Spierer's apartment building with her at around 2:30 am.

That "friend" was identified to the New York Post a as Corey Rossman, a fellow college student at the university.

The Post has more:

Students who encountered Spierer, 20, and her pal -- identified by friends as Corey Rossman -- leaving the building told The Post that she was drunk, he was bothering her and that he got angry when they asked him to stop.

"He was being overly aggressive . . . being so belligerent," one said.

But the two walked away together, winding up at Rossman's apartment, witnesses said.

Rossman, who the Post alleges has taken a polygraph test, said Spierer left his apartment around 4:30am. His lawyer claimed to the Journal News that Rossman has no memory of his last moments with Spierer because he was punched in an altercation at her apartment.

"At Smallwood [Spierer's apartment complex] someone confronted them," Rossman's lawyer, Carl Salzmann told the Journal News.

"He got punched in the face. He has no memory of that, or of the 15 minutes leading to that moment. The first memory he has is the next morning when he wakes up in his bed, and that's corroborated by several people."