PARIS — Priests in robes and hard hats worshiped Saturday at the Cathedral of Notre-Dame in the first Mass there since the French treasure was devastated by fire in April.

The priests were joined by a handful of workers and other worshipers, also in hard hats. The group was limited to about 30 for security reasons, and the solemn ceremony in Paris was shown live by a Catholic channel via YouTube.

The Mass was held in the Chapel of the Virgin, just off the choir. Visible as the camera panned across were a pile of charred timbers, all that remains of the attic’s interlocking wooden beams, and great gaping holes in the vault, caused in part by the spire’s fall.

Notre-Dame’s reconstruction is underway, though officials say the edifice is still being shored up. About 150 people now work at the site.