The National Gallery of Art has been evacuated after fumes from construction in the building made several people sick.
A firefighter and three museum guards have been hospitalized, complaining of nausea, headaches and other symptoms.
A busload of students visiting from Pennsylvania was taken to the hospital as a precaution after some of them complained of feeling ill.
The odor is believed to have come from sealant used in the construction work.
Etter says because much of the artwork is vulnerable to humidity, they can't flush the building's air by the usual method of having fans bring in fresh air. Instead, the building's ventilation system is being cranked up to do the job.
The National Gallery will be closed the rest of the day but should re-open tomorrow.
Etter says the incident is now a mass casualty event, though there are no serious injuries.
