The collapse was discovered early Wednesday morning at the Garber Facility in Suitland, Md., which houses artifacts from the National Air and Space Museum.
Smithsonian spokeswoman Linda St. Thomas says the collections are safe in a sealed container inside the building.
Emergency officials have told museum staff it's too dangerous to go in and check on the artifacts because the building is unstable.
St. Thomas says the facility includes buildings from the 1950s that were slated for demolition in the coming years. She says items stored at the building are not of high value, though it wasn't clear what collections were inside.
By Associated Press Writer Brett Zongker