Updated with details from Microsoft. After a bumpy New Year's weekend for Microsoft's Hotmail service, the company says it has fixed a problem that caused messages to disappear from an undisclosed number of email accounts.

It was "a limited issue that is now resolved," and the company apologizes to customers for any inconvenience, a company representative said via email.

"Microsoft is still investigating the root cause of what happened in this particular instance to prevent this from happening again," the company says.

Microsoft is declining to say exactly how many people were affected, but the Associated Press notes that the Hotmail support forums are showing hundreds of pages of complaints.

Update, 2:40 p.m.: In a blog post this afternoon, Windows Live exec Chris Jones writes that the issue affected 17,355 accounts. (Hotmail has about 360 million users total).

"Customers impacted temporarily lost the contents of their mailbox through the course of mailbox load balancing between servers," Jones writes. "We identified the root cause and restored mail to the impacted accounts as of yesterday evening, January 2nd."