Yahoo said Thursday it is investigating a security breach of its Yahoo user ID, in which some 450,000 Yahoo users' email addresses and passwords have leaked.

The company said in a statement that an "old file" from the Yahoo Contributor Network was compromised Wednesday. Among the stolen emails and passwords were many from Yahoo's own email service along with those of other companies. The Yahoo Contributor Network is a content-sharing platform. Yahoo said it is fixing the vulnerability that led to the disclosure, changing the passwords of affected Yahoo users, and notifying other companies whose users' accounts may have been compromised. D33D, a group of hackers, said it was responsible for the breach and claims that it took 453,000 accounts, according to an Associated Press report.

D33D said it hacked one of Yahoo's subdomains for the accounts. That subdomain is believed to be Yahoo Voices. Among the stolen accounts were email address from users on AOL, Gmail, Hotmail, Yahoo and others.

"We are still investigating," said a spokeswoman for Yahoo according to the Associated Press.