Police have matched DNA from a Yale research technician to evidence found at the crime scene on the Ivy League campus where graduate student Annie Le was found murdered this week, police sources reportedly said late Wednesday.

According to the New Haven Register, police have obtained, or are now in the process of obtaining, an arrest warrant against Raymond Clark III, 24, who had been named a "person of interest" in the case.

New Haven police spokesman Joe Avery said early Thursday that an arrest was expected "soon."

Officers are currently staked out at a motel Clark is staying at in Cromwell, about 25 miles north of New Haven, and are scheduled to hold a press conference at 8 a.m. ET where an arrest announcement is expected.

New Haven Police Chief James Lewis said earlier that charges will be filed against anyone whose DNA matches evidence found at the crime scene.

Authorities compared DNA taken from Clark's hair, fingernails and saliva with more than 250 pieces of evidence collected at the crime scene in New Haven, Conn., and from Clark's Middletown, Conn., apartment.

PHOTOS: Yale Graduate Student Murdered

Le's body was found on Sunday — the day her wedding had been planned for — stuffed into a wall of the lab building where she did research and to which Clark had access. Dr. Wayne Carver in a brief statement on Wednesday said an autopsy of Le determined that she was murdered by "traumatic asphyxia" due to neck compression.

Clark is not talking to police, Lewis said.

"At some point he may be willing to answer questions, but at this point he has invoked his rights," Lewis said. "He has an attorney. We couldn't question him if we wanted to."

Clark is a Yale staff member who did custodial work at the laboratory, such as cleaning mouse cages. He has three relatives — his fiance, his sister and brother-in-law — that do similar work at the Yale lab.

Clark and several other people have been under constant surveillance. The New Haven Police chief declined to say who those people were.

Two new search warrants were issued on Wednesday for a red Ford Mustang belonging to Clark and for other undisclosed items.

Clark was taken into police custody late Tuesday and released Wednesday at 3 a.m. after authorities collected DNA samples from him, questioned him and searched his apartment. No charges have been filed against him.

Clark said through his lawyer that he wanted to cooperate with the investigation. His attorney David Dworski said Wednesday his client is "committed to proceeding appropriately with the authorities." He would not comment further.

Clark lives in an apartment with fiancee Jennifer Hromadka, whom he plans to marry in December 2011, according to the couple's wedding Web site.

Among the possible motives detectives are mulling over is Clark's reported criticism of Le for her handling of the lab mice the two worked with, according to the New York Daily News.

Citing e-mails the pair reportedly exchanged, the Daily News said Clark had accused Le of failing to follow protocol when handling the mice, and she'd promised to do better.

Late Tuesday, capping a weeklong hunt first for Le and then for her killer, Clark was escorted out of his apartment and into a silver car. Neighbors leaned over the building's iron railings and cheered as police led him away.

New Haven Police Chief James Lewis declined to comment on reports that Clark's fiancee had contacted authorities Tuesday night when he came home with scratches, wearing different clothes than the ones he'd left for work in.

Hromadka, wrote on her MySpace page that she's not perfect, but cautioned people not to judge her.

"Who are you to judge the life I live? I know I'm not perfect and I don't live to be, but before you start pointing fingers make sure your hands are clean!!" the 23-year-old wrote.

The date of the MySpace posting is unclear. The page has since been taken down.

FOX News' Rick Leventhal and The Associated Press contributed to this report.

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