Bret Michael Edmunds, 26, remained in serious condition Saturday in a secure section of intensive care and under the guard of U.S. marshals.
"He is conscious, he is alert and he is speaking with them," Martinsburg City Hospital spokeswoman Teresa McCabe said.
Edmunds had checked himself into the hospital Thursday under a phony name after an apparent drug overdose. McCabe said Edmunds would remain at the hospital and would not be transferred elsewhere for several days.
Authorities have said Edmunds could be a witness and is not considered a suspect in the disappearance of Smart.
Edmunds, 26, who has no fixed address and was living out of his Saturn sedan, had been seen near the Smart family's neighborhood.
A milkman was able to partly recite his license plates. Those plates, stolen from another car, were found ditched Thursday along a road in Centerville, a suburb north of Salt Lake City.
The green Saturn was found at City Hospital in Martinsburg, W.Va., about 75 miles west of Baltimore. Elizabeth was not in the car, which West Virginia State Police photographed but did not enter before impounding it and towing it from the hospital, authorities said.
Police were awaiting a search warrant Friday evening.
Hospital officials said at a news conference Friday that Edmunds checked himself at 5:15 Thursday morning and was admitted to the critical care unit five hours later. They said Edmunds was in serious condition but would discuss his diagnosis or prognosis because of privacy rights.
Salt Lake City Police Chief Rick Dinse, who told reporters that Edmunds had drug-related liver damage, said police hoped Edmunds could be returned to Utah for questioning but said they would send officers to Martinsburg if he could not travel. Authorities were working quickly on details of how to question Edmunds because "there is a possibility that he could be critical to the point that he might not survive," the chief said.
In the meantime, Edmunds was being kept under guard in the critical care unit, whose three other patients were moved to other parts of the hospital.
Dinse stressed that Edmunds was not a suspect in Elizabeth's disappearance "at this time." He was arrested not because of his possible connection to the case but because he was wanted on outstanding charges of fraud and assault on a police officer in Utah and federal charges of unlawful flight, said Special Agent Dan Roberts of the FBI.
"He's a question mark, and we want to put a period on that question mark," the chief said.
But Dinse acknowledged in response to a reporter's question that police were interested in taping Edmunds' voice and playing it for Elizabeth's 9-year-old sister, Mary Katherine, who was in the bedroom at the time police believe a man abducted Elizabeth.
EDMUNDS TOLD INCONSISTENT STORY
Although Edmunds checked himself in through the emergency room early Thursday, it was not until Friday afternoon that hospital officials realized that he might be the man wanted for questioning in a case making national headlines 1,800 miles away.
Edmunds used a false name when he arrived, authorities said.
June 21-FBI and police officials in Utah discuss the arrest of Bret Michael Edmunds.
The FBI was notified of the hospital's suspicions Friday afternoon and needed barely an hour to confirm Edmunds' identity.
The discovery resolves one facet of a baffling case.
Police have administered polygraph tests to a number of people both inside and outside Elizabeth's family, authorities said Thursday. Police would not elaborate on what the polygraph tests found, and 16 days into a case they are investigating as an abduction, they said they still had no suspect.
Dinse said police had also searched the hard drives of 12 computers but had found nothing "that creates a nexus to this crime." Other officers said police examined computers owned by the immediate family and others.
FBI agents are looking at other kidnappings, including two teen-agers taken from the same apartment complex in Oregon and one in Idaho Falls, Idaho, that ended with the suspect's suicide, Roberts said. The abduction in Idaho Falls, which is about 190 miles from Salt Lake City, took place the same morning Elizabeth disappeared.
In addition, police said they were aware of one e-mail ransom note, but Dinse said they considered it a hoax.