Police do not yet know what caused the death of Phylicia Barnes, a star student from North Carolina whose naked body was found in a Maryland river Wednesday, or the death of a black male whose unclothed body was found three to four miles downstream.
Barnes, missing since late December, has been the subject of a multi-jurisdictional missing persons investigation since at least January, officials said.
"We're now at stage one of a new phase of the investigation," Baltimore Police Commissioner Frederick Bealefeld told reporters this evening. "There's a mountain of investigative work that needs to be done."
Preliminary autopsies failed to determine what caused the deaths of Barnes or the unidentified male, said Terrence Sheridan, superintendent of the Maryland State Police, and there was no evidence linking the two deaths other than the proximity of their bodies.
"There was no indication of any overt wounds or injuries to Phylicia Barnes' body," Sheridan said.
"Nothing was found on the bodies, attached to the bodies when we recovered them from the river," he added.
For more on the Barnes case, see ABC News coverage of her disappearance.
Anthony Guglielmi of the Baltimore Police confirmed Thursday that investigators found not one, but two bodies Wednesday near the Susquehanna River about 35 miles from Baltimore.
One was that of the 16-year-old Barnes, who was identified via dental records, Sheridan said.
The identity of the second body -- a 6-foot-4, 240-pound, black male -- was not immediately clear. Police were trying to identify him through fingerprint records, Sheridan said.
Workers at the Conowingo Dam spotted Barnes' body floating in the water around 7:30 a.m. Wednesday and notified state troopers in the area, according to Maryland State Police spokesman Greg Shipley. While investigators were still in the area, they discovered a second body floating three or four miles south of the dam a few hours later.
Barnes was 16 when she went missing Dec. 28 during a trip to visit her half-sister. She would have turned 17 in January.
"The medical examiner has indicated to us that it's not out of the realm of possibility that the body could have been there" in the river since the time of Barnes' disappearance, Sheridan said.
The cold water could have preserved the body, he said, and the swiftness of the river flow may make it difficult to learn where Barnes entered the river.
"When you look at that river, how fast it's moving when the floodgates opened, anything could have happened," Sheridan said.
Barnes was from Monroe, N.C., a straight-A student, and was last heard from Dec. 28, 2010, via Facebook, when she posted a note saying she was at her sister's apartment with her sister's boyfriend.
Hundreds went to the Facebook page "Pray for Phylicia Barnes," leaving notes of condolences after police announced her body was discovered.
"R.I.P Phylicia...we pray for peace with your family and justice served for the person or persons responsible for ending your life," one Facebook user wrote.