Posted Wednesday, June 6, 2012 --- 10:45 a.m.

LONDON (AP) -- Business social network LinkedIn says it is investigating reports that more than six million passwords have been stolen and leaked onto the Internet.

Graham Cluley, a security expert with Sophos, said in a blog post that a file containing more than six million encrypted passwords has been posted on the Internet and hackers are working together to crack them.

He said Wednesday that investigations by Sophos researchers have confirmed that the file does contain, in part, LinkedIn passwords. Cluley recommended LinkedIn users change their passwords "as soon as possible."

LinkedIn did not respond to repeated requests for comment but the company posted a tweet saying that its team is "looking into reports of stolen passwords."

Copyright 2012. The Associated Press.