A week after confirming many of its passwords had been leaked online, business networking site LinkedIn has sought help from the US Federal Bureau of Investigation to look into the matter.

LinkedIn's Vicente Silveira said the company is taking more steps to protect its users, amid earlier reports some 6.5 million passwords were stolen last week.

"We take this criminal activity very seriously so we are working closely with the FBI as they aggressively pursue the perpetrators of this crime. As you may have heard, there have been reports of other websites that have suffered similar thefts. We want to be as transparent as possible while at the same time preserving the security of our members without jeopardizing the ongoing investigation," Silveira said in a blog post.

But he maintained the compromised passwords were not published with corresponding email logins.

At the time they were initially published, he said majority of those passwords remained hashed or encoded, though some of the passwords were decoded.

"Again, we are not aware of any member information being published at any time in connection with the list of stolen passwords. The only information published was the passwords themselves," Silveira added.

So far, Silveira said there have been no reports of member accounts being breached as a result of the stolen passwords.

Citing LinkedIn's initial investigation, Silveira said "all member passwords that we believe to be at risk have been disabled."

"Based on our investigation, those members whom we believed were at risk, and whose decoded passwords already had been published, had their passwords quickly disabled and were sent an email by the Customer Service team," Silveira said.

By end-Thursday, Silveira said all passwords on the published list that may have been at risk had been disabled.

On the other hand, Silveira said LinkedIn already adopted several security layers for passwords. — TJD, GMA News