The breached records contained personal information of about 206,000 associates, timeshare owners and timeshare customers, the company said this week in a statement.
Stephen P. Weisz, Marriott Vacation Club International president, said the company was assisting affected customers.
"We regret this situation has occurred and realize this may cause concern for our associates and customers," he said. "We have recently mailed notifications to associates, timeshare owners and timeshare customers and are available to answer any questions they may have."
Marriott has offered affected individuals free enrollment in a credit monitoring service and notifications of credit report activity. The company also launched an investigation of the incident and notified government officials.
Peter J. Watzka, chief customer officer with Marriott Vacation Club, said in a letter to customers with missing credit card information that his company does not yet have much information on the missing tapes.
"For many years, as part of our company's processes of protecting computerized data, we have regularly prepared back-up copies of our data tapes for storage at a secure offsite facility," he said. "We recently determined that a set of these back-up tapes cannot be located. Despite our ongoing investigation of this incident, the tapes have not been found."