Officials at Christie’s auction house said on Saturday that the marquee sales that account for nearly half of its annual revenue would continue, despite the company having lost control of its official website last Thursday in a hack that is testing the loyalty of its ultrawealthy clients amid its spring auctions.

Natasha Le Bel, a spokeswoman for the auction house, said that Christie’s New York sales of modern and contemporary art “will take place as planned,” but did not respond to questions of how the online portion of the auction would continue. “We remain committed to providing the highest level of service to our clients and look forward to a successful week,” she said.

On Thursday, Christie’s experienced what it called a “technology security issue” that took its company website offline, leaving in place an apology and the promise to provide “further updates to our clients as appropriate.” By Sunday, the site was still down.

It was the second time in less than a year that Christie’s had suffered a breach. In August, a German cybersecurity company revealed a data breach at the auction house that leaked the locations of artworks held by some of the world’s wealthiest collectors.

Over the weekend, dozens of those potential buyers gathered at the company’s galleries at Rockefeller Center in Manhattan to view the expensive artworks that have a total high estimate of nearly $840 million, and to discuss bidding. Employees led private tours past the giant Andy Warhol “Flowers” silk-screen painting from 1964 that carries a high estimate of $30 million, and down toward the more modestly priced day sales, where a Barbara Kruger artwork proclaiming “You can’t drag your money into the grave with you” had a high estimate of $600,000.

Christie’s employees assured some clients in the galleries that its website would be fixed “imminently,” but on Saturday afternoon, when the company still had not regained control, it replaced a temporary landing page on the site since Thursday with another temporary website produced through a free web design company called Shorthand. The temporary site lets viewers browse online catalogs of upcoming sales but does not allow online bidding or registration.