Raymond Clark, the "person of interest" in the murder of Yale grad student Annie Le, was released from police custody early today after investigators took DNA samples from him and searched his apartment until shortly after dawn today.
"He's not under arrest. We can't hold him," said New Haven Police Department spokesman Joe Avery. "He was only made to comply with the warrant."
Clark, a 24-year-old technician at the Yale lab where Le's body was found Sunday, was taken into custody by police about 10:30 p.m. on a warrant that allowed detectives to take DNA samples. Clark, who is not a Yale student, cooperated and was released around 3 a.m., Avery said.
At a news conference Tuesday evening, New Haven, Conn., Police Chief James Lewis said two search warrants were served, one on the residence and one on Clark himself, indicating investigators were seeking DNA evidence from saliva, hair and fingernails.
"We took him into custody to gather evidence from his body and his person," Lewis said.
Investigators tailed Clark for days, reportedly sending as many as 15 FBI agents to follow him at a local fair over the weekend.
Approximately 150 pieces of evidence were collected from the crime scene. Clark's sister, brother-in-law and fiancee, Jennifer Hromadka, also worked in the lab building but did not go to work today.
Police cars were parked all day outside Clark's apartment complex in Middletown, Conn., about 20 miles from Yale. Neighbors said surveillance cars have been at the complex for at least 24 hours.
One of Clark's neighbors, Felicia Diaz, told ABC News she saw Clark and his fiancee leaving their apartment in a hurry the same day Annie Le's body was discovered.
"I thought it was kind of suspicious where I thought he was moving out or something because it was a lot of luggage," Diaz said. "So I really didn't know what was going on."
ABC News consultant and former FBI agent Brad Garrett said that though he had been investigated by authorities for days, it's likely police did not take Clark into custody sooner because he was not a threat to other students.
"If you do not believe they are a danger to anyone else, then you may let him go," Garrett said. "If this is a crime of passion, you're not concerned about anyone else."
Sources have previously described a suspect as being a lab technician who worked in the same building where Le studied. The suspect has what appears to be defensive wounds on his chest, suggesting a violent struggle. Sources also said the man failed a polygraph test.
Le had been seen entering the Amistad Street lab around 10 a.m. on Tuesday but none of the cameras caught her leaving. Her body was found shortly after 5 p.m. Sunday, shoved into a space in the wall meant to conceal pipes and wiring.
The medical examiner did an abrupt about face Tuesday and withheld Le's autopsy results, which would have revealed the woman's exact cause of death.
The medical examiner's office said it was being withheld at the request of the New Haven State's Attorney. The state's attorney did not immediately respond to ABCNews.com to explain his decision.
"One of the reasons you do not release autopsy reports is you, as the medical examiner, want to have as much information as you can before you make that report," Garrett said. "[Clark] may make statements to police, or they may find evidence that would adjust the final report."