A DNA test has linked Raymond Clark III to the murder of Annie Le GRD ’13, and Clark is expected to be arrested this morning, according to a person familiar with the investigation.

Clark, 24, who works at Yale as an animal lab technician, was first detained late Tuesday night, when authorities called him a “person of interest,” served him with two search warrants and took a DNA sample. He was released at 3 a.m. Wednesday and served with two more search warrants.

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The source said Clark’s DNA matched a piece of evidence taken from the Yale research facility at 10 Amistad St., where Le was strangled to death Sept. 8 and where her remains were found Sunday, which was supposed to be her wedding day.

New Haven Police Department Chief James Lewis said at a press conference Wednesday afternoon that police have collected 250 pieces of physical evidence, interviewed 150 people and watched 700 hours of video footage as part of the investigation to date. He said the DNA tests had been expedited and that he believed “the case is going to end in arrest.”

At the same time Lewis was speaking, authorities were standing outside the Super 8 motel in Cromwell, Conn., where Clark was staying at the time. Investigators have been monitoring Clark since at least Sunday, when New Haven police took over the homicide case, Lewis said Tuesday night.

Reached Wednesday, Clark’s lawyer, David Dworski, said, “We are committed to proceeding appropriately with the authorities, with whom we are in regular communication.” He declined further comment.

One of Clark’s colleagues in the Animal Resources Center said neither Clark nor his sister, brother-in-law or fiancée have shown up for work since Le’s body was found. That colleague said Clark has worked at Yale for two or three years, while Clark’s sister and her husband have been employed by the University for six or seven years.

The colleague, who was told not to talk to the press, said Clark tended to laboratory animals and cleaned their cages in the basement of 10 Amistad St., so he would have been intimately familiar with the floor where Le’s body was found behind a wall.

Richard White, an architect who was consulted on the design of 10 Amistad St., said the mechanical chase in which Le’s body was found had thicker walls than the rest of the building for fire code reasons.

Because chases connect the building’s different floors, he said, the walls would be unusually thick and probably have steel framing. In an address to the medical school community Monday afternoon, University President Richard Levin explained that the material of the wall made it difficult for bloodhounds or humans to locate her.

“It was only after a number of days that the scent became detectable,” Levin said.

White added that there are locks on the chases in the building, though he said they would be about the same quality as regular door locks.

“They’re not terribly secure,” he said, “but they’re secure enough for an honest person.”

The motive for Le’s killing remains unclear. University President Richard Levin, addressing a news report that Clark sent e-mails to Le before her death, said, “To my knowledge there’s nothing that would be relevant to the case” in the correspondence between the two.

Other reports have suggested that Clark had complained about the way Le treated her lab animals. But two University officials called those reports false.

“I’ve not heard anything like that in the entire course of this investigation,” Yale Police Department Chief James Perrotti said.

A high-ranking Yale official added that the University has no record of a complaint filed against Le by anyone, including Clark, concerning her laboratory conduct.

What is known about the case is that Le was last seen entering the 10 Amistad St. building at 10 a.m. on Sept. 8, after leaving her keys, purse and phone in her office at the Sterling Hall of Medicine. She was considered a missing person until Sunday, when her body was found and the case became a homicide.

Le’s family and fiancé, Jonathan Widawsky, have not spoken publicly but issued a statement Tuesday thanking the community for its support and sensitivity.

Zeke Miller contributed reporting from Cromwell, Conn., and Colin Ross contributed reporting from New Haven.