GAINESVILLE, FLA., SEPT. 10 -- More than 500 pieces of evidence are being examined in the killings of five college students, but investigators refused to say today if they are closer to an arrest.

"We're not going to let time dictate this investigation," said Lt. Spencer Mann, spokesman for the Alachua County Sheriff's Office. "We have to be right. We can't guess. We can't take chances."

Only about half of the evidence, which authorities characterized last week as "promising," has been processed at the crime laboratory of the Florida Department of Law Enforcement in Jacksonville, said Steve Platt, who heads the lab.

The evidence was gathered from the three slaying scenes and during searches of suspect Edward Lewis Humphrey's Gainesville apartment, Indialantic home and his car, authorities said. The evidence also includes bodily fluids and fingerprints taken from Humphrey at the Brevard County Jail in Sharpes.

He is being held in lieu of $1.1 million bond on unrelated assault charges.

"It's a slow, painstaking effort," Platt said of the crime-scene evidence. "We are faced with what can be likened to three very complex puzzles that we are trying to put together one piece at a time."

DNA testing of blood and semen are in progress, Platt said, although investigators refused to say whether that evidence was obtained from the crime scenes or from Humphrey.

Humphrey is one of eight suspects, police said. The only other publicly identified is Stephen Michael Bates, 30, a short-order cook, also jailed on an unrelated assault charge.