NEW YORK (AP) — It has happened again. And this time, the victims are some of the people who use Yahoo.

The company says the usernames and passwords of some of its email customers have been stolen. And, Yahoo says, the critical information has been used to gather personal information about the people those Yahoo mail users have been in touch with recently.

Yahoo isn’t saying how many accounts have been affected. But the research firm comScore says Yahoo is the second-largest email service worldwide, after Google’s Gmail.

There are 273 million Yahoo mail accounts worldwide, including 81 million in the U.S.

Copyright 2014 The Associated Press.