Alcatraz Island will be closed this week while crews repair the island’s dock, temporarily cutting off access to one of San Francisco’s best-known tourist destinations, according to the National Park Service.

The closure began Monday and was scheduled to last through Friday. In an alert posted Friday, the Park Service said, “Access to the island is temporarily closed for dock repair.”

All scheduled tours have been refunded, the Park Service said. Visitors who want to reschedule are being directed to contact Alcatraz City Cruises, the official ferry operator.

The Park Service did not say what prompted the repairs or whether service would resume immediately after Friday. It did not immediately respond to a request for comment.

But for now, the temporary shutdown means no public access to the island during a week that would ordinarily draw spring visitors to one of the city’s marquee attractions.