Dr. Wayne Carver's office released the results three days after the body of 24-year-old Annie Le was found in a Yale medical school research building. Carver had previously announced Le's death as a homicide.
Police released a Yale University animal research technician from custody Wednesday after collecting DNA samples and questioning him in Le's killing.
Raymond Clark III was taken into custody Tuesday night at his apartment in Middletown, Conn., and was released into the custody of his attorney early Wednesday, New Haven police said.
Clark's attorney, David Dworski, of Fairfield, said Wednesday his client is "committed to proceeding appropriately with the authorities." He would not comment further.
Investigators are hoping to figure out within days whether Clark can be ruled out as the killer.
Clark has been described as a person of interest, not a suspect, in Le's death. Her body was found Sunday, which was to have been her wedding day.
Clark and and his fiancee, Jennifer Hromadka were both animal research technicians in the lab where Le worked.
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.
Overnight, state police officers sorted through items on a card table set up outside Clark's ground-floor apartment's door.
A tow truck took away a red Ford Mustang neighbors say was used by Clark.
A resident of the complex, Rick Tarallo said he, his wife and 6-month-old daughter live in a unit next to Clark and his fiancee, Jennifer Hromadka.
He said the couple was "really quiet" and lived with an older man, whom he speculated was one of their fathers.
"He seemed like a good guy," Tarallo said of Clark. "They didn't strike me as someone who would try to kill somebody."
Police started tearing down the yellow crime scene tape as daylight broke Wednesday. Neighbors said they hadn't seen Hromadka in the area for days.
Loraine Falcon, 32, a nurse aid who lives in Clark's building, said the police activity kept her and her three kids - ages 15, 10 and 8 - up much of the night and left her fearful for their safety.
"I just want to know if he did it," Falcon said.
Clark's apartment appeared empty Wednesday morning after police left. No one answered the door. The brown flowered doormat remained.
During the search, one officer commented that the apartment smelled like animals. Multiple neighbors said they saw Clark and Hromadka load luggage, cats and two rodents into a vehicle on Saturday.
Falcon said she also saw Clark loading a suitcase and a duffel bag into a car Sunday at about 5 p.m.
New Haven police Chief James Lewis said police were hoping to compare DNA taken from Clark's hair, fingernails and saliva to more than 150 pieces of evidence collected from the crime scene. That evidence may also be compared at a state lab with DNA samples given voluntarily from other people with access to the crime scene.
"We're going to narrow this down," Lewis said. "We're going to do this as quickly as we can."
Police have collected more than 700 hours of videotape and sifted through computer records documenting who entered what parts of the research building where Le was found dead.
Le worked for a Yale laboratory that conducted experiments on mice, and investigators found her body stuffed in the basement wall of a facility that housed research animals.
In addition to Clark and Hromadka, Clark's sister and brother-in-law were also technicians at Yale's Animal Resources Center, according to Yale records.