The presentation by Patricia Worsham came Thursday during a meeting of scientists and experts who are part of an FBI-commissioned panel tasked to study the science behind the investigation of the anthrax mailings, also known as Amerithrax.

Ivins, a leading anthrax researcher at Fort Detrick's U.S. Army Medical Research Institute of Infectious Diseases, died a year ago of an apparent suicide after the FBI identified him as the sole suspect in the letter attacks.

The FBI has yet to officially close the case, but the agency's forensic science methods are already being studied by a group of scientists working under the National Academy of Sciences.

The FBI is funding the 18-month, $880,000 NAS study, which will affirm the validity of the investigative science, but will stay clear of examining how the FBI connected Ivins to the crime.

On Thursday, the 15-member panel questioned the analysis and tests scientists used to isolate the RMR-1029 strain, which came from an Ames strain turned into powder form and mailed in letters that killed five people and sickened 17.

The flask of RMR-1029 anthrax under Ivins' control was identified as the origin of the bacteria used in the letters.

Worsham, who works in USAMRIID's bacteriology division, said she was prevented by a federal gag order from talking about certain aspects of the case involving Ivins. Instead, she presented how the lab identified morphological variants to identify the strain used in the attack.

During the investigation, federal agents enlisted the help of multiple agencies and organizations, including scientists at USAMRIID.

"We had to send every Ames strain we had to the repository," Worsham said.

She said the Ames strain was valuable to the work at USAMRIID because it worked well for vaccine tests. Ivins was a leading scientist in developing an anthrax vaccine.

"Ames had a good history," she said. "It had not been passed through the laboratory a great deal."

Paul Keim, a Northern Arizona University biology professor, explained to the panel how his team identified the anthrax Ames strain among nearly 2,000 strains collected.

Although researchers could only identify four or five new isolates from the Ames strain, Keim said he was positive about the match between the anthrax collected from the letters and the flask under Ivins' control.

"It would have been nice to have 100 isolates," he said.

Keim said he had criticism for the FBI, which used his lab as a repository for evidentiary samples.

"We weren't able to get money from the FBI to do these analyses until May 2002," he said. "For the next crisis it would have been nice if the federal government had a few sugar grants."

Post your comments » Round 2: Snow expected to fall today, Wednesday Fast on the heels of the largest 24-hour snowfall to hit the Frederick County since 1983, meteorologists are predicting another round of heavy snow and wind to hit today. The National Weather Service issued a winter storm warning Monday afternoon for the area, including Frederick County, and said 10 to 20 inches of snow is possible by Wednesday night. Weather-related closings, delays A list follows of weather-related closings and cancellations for this week. Fire and police blotter Police search for robber School closures cause makeup schedule revision Even though Frederick County Public Schools are closed today -- using the sixth snow day this school year -- the school system will not hold school on the Monday Presidents Day holiday as the first scheduled snow makeup day. Crowds pay respect to fallen marine Even U.S. Marines couldn't hold back tears Monday at the viewing of their colleague, Sgt. David Smith. The procession to the Frederick Christian Fellowship Church was led by Frederick County Sheriff's deputies. Dressed in full military regalia, Marines carried Smith's casket into the church followed by family members as more Marines stood at attention.