Three National Zoo employees were dizzy and nauseated from exposure to rat poison left in the red panda yard. Before they received medical attention, they were told not to tell the ambulance crew what had happened or that they worked at the zoo.

The ambulance did not come into the zoo. Instead, the zoo workers, sickened last year, were driven to a Metro station to meet the vehicle. One employee was told to cover a zoo insignia with a jacket before going to the hospital.

Employees provided those accounts to an investigator from the Smithsonian Institution's inspector general's office, which was looking into the deaths of two red pandas that ate the rat poison in their yard in January 2003.

The inspector general's report says that when the zoo called D.C. Fire and Emergency Medical Services for help, it asked that the hazardous materials unit be "discreetly dispatched."

But the report, obtained recently by The Washington Post, does not delve into the city's response or explain how the instructions to the employees came about.

The employees told the investigator that they got their directions from a fire department team that was called to the zoo.

Large portions of the copy of the report that was provided to The Post -- including names -- were blacked out because of privacy and other concerns. The accounts of the employees were in a heavily redacted attachment to the report that summarized their statements.

Neither the zoo nor the city could explain this week why there would have been a need for secrecy. Zoo officials said the fire department was in charge of the medical response. A city official said he was unable to confirm that anyone from the fire department gave the instructions to the zoo employees.

"We have no documentation" of these instructions, said Alan Etter, a fire department spokesman. "I can't imagine anyone advising them to do this. . . . Maybe the employees were confused."

Etter said an ambulance typically would have gone to the zoo to transport the sick employees, unless its crew was told to go to the Metro station. He said the initial call from the zoo did not say there was an emergency.

"No one indicated there were sick people," he said. "No one indicated there were dead animals."

When the department's hazardous materials unit arrived at the zoo and realized there were sick employees, Etter said, it called for an ambulance.

The zoo said the fire department made all decisions about transporting the employees.

"We do not know the precise nature of the original call from the zoo employee to D.C. Fire/Hazmat, but we assume if he or she asked that they be discreet, it was to avoid public panic," Linda St. Thomas, a Smithsonian spokeswoman, said in an e-mail.

The dispatcher's log shows that the call sought to "assist zoo personnel in odor identification" as the zoo sought to determine whether poisonous gas was still present in the exhibit.

The zoo called for help shortly after 1 p.m. Jan. 11, 2003, about four hours after a keeper found the dead pandas. Most employees did not know that a pesticide contractor had buried poison pellets in the animals' yard the previous afternoon, according to the inspector general's report. Those workers on the scene that morning rushed to the enclosure, pulled the red pandas from public view and began probing the animals. They also looked down ratholes and combed the yard for BB pellets, rocks or other signs of what might have killed them.

By the time employees learned about the poison, some were feeling sick and having trouble breathing.

One employee told the investigator about experiencing "severe cramps" and being instructed to go to the hospital. The employee was taken to a Metro station off Connecticut Avenue NW to wait for an ambulance, according to interview notes. The employee quoted a firefighter as saying that the ambulance crew was not to be told what was wrong or that the worker was from the zoo.

When the ambulance arrived, the person who had radioed for it "told the crew that the 'patient' was found on Connecticut Ave. and needed to be transported to George Washington University Hospital," according to the interview notes. The zoo employee "would not tell them what had happened despite the crew's obvious concern for their own safety."

For about a half-hour, the ambulance waited at the Metro station for two other zoo employees. According to interview notes, these employees said they also were told not to talk with anyone "either in the ambulance or the emergency room," but to speak only to a particular doctor at the hospital.

The inspector general investigated the panda deaths after the pesticide contractor, denying any responsibility, alleged that the incident was a deliberate act of sabotage by some zoo employees who opposed killing rodents. The report said the allegation of sabotage "was not substantiated."

Laboratory tests showed that the pandas died after eating tiny pieces of the poison that apparently fell on the ground while the pellets were being buried.

The inspector general's "Close Out Synopsis" of the investigation does not mention the statements by the ailing zoo employees, except to say that they were taken by ambulance to the hospital for observation and released the same day.

In other interviews, a zoo employee told the inspector general that "rats were everywhere" in the month before the poison was buried in the panda yard. Bait boxes posed a problem because rats and squirrels would drag the bait from the boxes into animal enclosures or public areas. One keeper told of seeing a child carrying a packet of the poison.

The report was among records released to The Post, which requested them under the Freedom of Information Act. The Smithsonian, which oversees the zoo, contends that it is not subject to FOIA, but the inspector general provided the records "in accordance with its mandate to increase and diffuse knowledge and consistent with its trust responsibilities."

Staff writer James V. Grimaldi contributed to this report.