Employees in a mail-sorting room at the Los Gatos main post office at 101 S. Santa Cruz Ave. reported smelling a chemical odor like that of a bug spray at approximately 11 a.m., said Santa Clara County Fire Department spokesman Dennis Johnsen. Several also reported a metallic taste in their mouths, white blotches on their skin and shortness of breath.

Though firefighters and paramedics talked with about 25 to 30 people who were in the area at the time, most refused treatment. Only four postal workers were taken to the hospital, in addition to one customer who was in the post-office box section adjacent to the sorting room. Johnsen said a postal employee also drove to the hospital before emergency personnel even arrived at the scene.

S. Santa Cruz Avenue south of Main Street and the Los Gatos Town Plaza directly in front of the office were closed off to the public for about five hours as county fire crews treated and decontaminated 15 people. Other local businesses remained open.

Hazardous materials crews and FBI investigators combed the building multiple times both that day and the next, but came up empty-handed.

"Whatever was there, because there was definitely something there that morning, has dissipated, and we do not know what it is," Johnsen said.

The post office was reopened to employees at approximately 4 p.m., and opened to customers again the next morning.

According to Doug Marshall, acting postmaster at the Los Gatos office, all of the postal workers who were regularly scheduled to work the next day, including those who were hospitalized, reported for work Sept. 15.

"The morale seemed to be high," Marshall said. "There didn't seem to be any trepidation."

Johnsen said no packages were found to contain the offending chemical, allaying fears that one was sent illegally through the mail. Dr. Vincent Marinkovich, a Redwood City immunologist locally renowned for his expertise in treating patients exposed to mold and microtoxins, said those agents could be responsible for the symptoms.

But a large number of spores would have had to be released for multiple people to experience the same symptoms, he said.

The employee who maintains the ventilation system was there that morning, and investigators walked him through the building. They determined he did not do anything that would have caused a chemical or toxin release.

Marinkovich said the symptoms could have come from exposure to any number of chemicals. Some of the symptoms could even be reactions to the others.

"A lot of it could be some anxiety involved there," he said. "The psychology of suddenly having a metallic taste in your mouth may make you breathe hard."

The employees recovered quickly, Marshall said, as did the 13 routes that did not receive mail on Sept. 14. Additional carriers from post offices in Campbell, Cupertino, Milpitas, San Jose and Santa Clara assisted in delivering the delayed mail the next day. He said no special instructions were given to postal carriers or mailroom employees.

"They're just looking out as they normally do," Marshall said. "We're normally suspicious."

The same day, a private company in San Mateo received a letter containing white powder and threatening to contain anthrax. San Francisco bureau FBI spokeswoman LaRae Quy said federal investigators determined that the powder was anthrax, and that the two incidents were unrelated. She also said investigation of the Los Gatos incident has been turned over to the U.S. Postal Service.