Investigators have found the body of a female inside a wall in the basement of 10 Amistad St., the building where Annie Le GRD ’13 was last seen, authorities said Sunday evening.

At a press conference at New Haven Police Department headquarters, NHPD Assistant Chief Peter Reichard said the remains were found shortly after 5 p.m. on Sunday, adding that he could not confirm whether the remains were Le’s. Still, he said, authorities are now classifying the case as a homicide investigation.

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“She hasn’t been identified, but we’re assuming that it is [Le] at this time,” Reichard said.

In a campuswide e-mail titled “Tragic News,” University President Richard Levin said an autopsy to identify the body will be performed by the state Office of the Chief Medical Examiner.

The news comes a day after officials said they seized bloody clothes from a ceiling at 10 Amistad St., where Le was last seen. A source within the Yale Police Department said the clothes are not what Le was wearing when she entered that facility Tuesday, adding that the blood on the material could be either human blood or animal blood, since many animal experiments are conducted in the research facility.

The official, who spoke on the condition of anonymity to discuss an ongoing investigation, said officials are currently analyzing the blood to determine its origins.

Le started her Tuesday morning working in the Sterling Hall of Medicine, where her lab was located, Yale Vice President and Secretary Linda Lorimer said.

Le left the lab around 10 a.m. to walk to 10 Amistad St. three blocks away, where she frequently went to conduct experiments, Lorimer said. A surveillance photograph distributed by the YPD shows Le entering the building at 10 Amistad St. on Tuesday morning. University officials have yet to locate Le exiting the building.

FBI Special Agent Kim Mertz said Saturday that authorities have spoken to “numerous people” who saw Le inside the facility at 10 Amistad St. but declined to give any further details.

A fire alarm that sounded in the Amistad Street facility at 12:40 p.m. on Tuesday is thought to have been a false alarm, Mertz said. Someone working in the lab produced steam that tripped the alarm, she said.

Le, who was scheduled to be married on Sunday, left her purse containing her cell phone, credit cards and money in her office in Sterling, Lorimer said. Her wedding has since been canceled.

Le’s family and fiance, Columbia University graduate student Jonathan Widawsky, are cooperating with the investigation. On Saturday, officials asked that the media respect the family’s privacy.

Investigators combed 10 Amistad St. for clues last week, questioning friends, faculty and colleagues. More than 100 law enforcement officials from four different agencies — the New Haven Police Department, the Yale Police Department, the Connecticut State Police and the Federal Bureau of Investigation — are involved on the case, University officials said.

As part of the investigation, authorities undertook several complete sweeps of 10 Amistad St., bringing in bloodhounds and even combing through trash in a dumpster outside the building.

Reporting was contributed by Isaac Arnsdorf, Zeke Miller, Martine Powers and Victor Zapana.