Denver ? A national system to trace biological crimes may soon make it more difficult to stage bioterrorism attacks without getting caught.

The Federal Bureau of Investigation and prominent microbiology organizations announced guidelines Sunday for conducting criminal investigations of biocrimes, including cases such as the “anthrax letter” attacks in the fall of 2001 and incidents in which a person infected with HIV intentionally exposes others to the virus. The announcement was made at the annual meeting of the American Association for the Advancement of Science.

“It’s much easier now than ever to perpetrate a crime,” said Bruce Budowle of the FBI. But law enforcement officials often have difficulty linking the crime to the criminal. No arrests have been made in the anthrax letter case, in which five people died of inhalation anthrax after breathing spores that leaked from letters.

More than a year passed before intentional food poisonings in Oregon and Texas were recognized as crimes instead of naturally occurring disease outbreaks, he said.

The government hopes to establish a national BioForensics Analysis Center at Fort Detrick, Md., Budowle said. But clinical laboratories in hospitals, state and local health departments, veterinary offices and universities may be the first to recognize an attack with a biological agent. Workers at those labs should be properly trained and certified to collect evidence for use in a criminal investigation. New standards that establish the reliability of forensic tests will be necessary if such tests are to be used in court, Budowle said.

The government also plans to build a database of bacteria and viruses for comparison with microbes used in biological crimes.