Roof collapses at Smithsonian warehouse in Md.

Historic aircraft and spacecraft were exposed to freezing temperatures Wednesday after heavy snow collapsed part of a roof and wall at a Smithsonian Institution storage facility.

No artifacts were thought to be damaged because they are all kept in boxes or protective crates, though some pieces usually are kept at stable temperature and moisture levels, officials said.

The metal building, part of the Garber Preservation, Restoration and Storage Facility in Suitland, houses about 1,500 artifacts from the National Air and Space Museum, including parts of aircraft and spacecraft and about 800 pieces of aviation and space-themed artwork.

“Right now, the building is still standing,” said museum spokeswoman Claire Brown, adding that shelving units inside were supporting the structure. “We’re confident the portion of the collection that’s in there is OK.”

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The flown artifacts could be from any era, ranging from the space shuttle program to Apollo or earlier, she said. All the pieces are considered valuable, Ms. Brown said, but curators didn’t identify any piece as more valuable than others.

Emergency crews shut off power and natural gas service to the building when the collapse was discovered early Wednesday, Prince George’s County fire department spokesman Mark Brady said. Authorities determined the building was unstable but weren’t sure what artifacts were inside.

“At this time, they are exposed to some of the elements,” Mr. Brady said.

Artwork in the building, including posters, paintings and sculpture, was kept in a sealed, insulated box, Ms. Brown said. There was no other power source for the building. Curators noted, though, that they usually keep artifacts at cool temperatures for preservation purposes.

“At this point, we’re not worried about the falling temperatures or any other risks associated with the power being cut to the collection,” Ms. Brown said.

A collection of historic spacesuits from Apollo moon walks is kept in a secure building nearby but was not affected.

The expansive museum storage and processing facility in Maryland includes buildings from the 1950s, Smithsonian spokeswoman Linda St. Thomas said. The building that collapsed was set for demolition in the coming years, and many air and space artifacts will be moved to a new restoration facility in Virginia.