Washington ? Months after anthrax-tainted letters killed five people and sickened more than a dozen, the FBI said Monday that its investigators do not have a prime suspect despite conducting hundreds of interviews.

“There is no prime suspect in this case at this time,” spokesman Bill Carter said.

White House spokesman Ari Fleischer said there are several suspects and the FBI has not narrowed that list down to one.

President Bush wants the case resolved quickly, Fleischer said, but also wants the FBI to take its time and “build a case that would stand in court, that is thorough, that is conclusive.”

The FBI  renowned for its behavioral profiles of criminal suspects  does have some clues about the suspected anthrax-mailer, according to an earlier letter from the lead FBI investigator to a group of scientists.

Van Harp, assistant director of the bureau’s Washington office, wrote that the FBI believes that a single person, with experience working in a laboratory, is behind the mailings. Harp described this person as having “a clear, rational thought process and appears to be very organized in the production and mailing of these letters.”

Fleischer said the source of the anthrax definitely was domestic, and the block handwriting on the letters seemed “chosen by design” to throw off investigators.

Harp also said the FBI believes that, because the mailed anthrax was of the so-called “Ames strain” of Bacillus anthracis, the suspect probably has or had legitimate access to biological agents in a laboratory. Harp also described the suspect as “standoffish” and preferring to work alone rather than in groups.

“It is possible this person used off-hours in a laboratory or may have even established an improvised or concealed facility comprised of sufficient equipment to produce the anthrax,” Harp said.