Social media giant Facebook have said hackers accessed data from almost 30 million accounts.

Facebook said 29 million accounts were hacked, as part of a security breach that was disclosed two weeks ago, reports standard.co.uk.

This is the first time the exact number has been known, as Facebook originally said 50 million accounts could have been affected.

The hackers accessed names, email addresses or phone numbers from those 29 million accounts, the company said.

For 14 million of those accounts, hackers got even more data, such as hometown, birthdate, the last 10 places they checked into or 15 most recent searches.

One million accounts were also affected, but hackers did not gain any information from them.

Messages, Facebook said, will be sent to those who have been affected by the hack.

Third-party apps and Facebook-owned apps like Instagram and Whatsapp have remained unaffected, the company said.

It is the worst breach in the company’s history and appears to have been carried out by an unnamed attacker.

Facebook said the FBI is investigating the major security breach, but added the authorities asked it not to discuss who may of been behind the attack.

When Facebook disclosed the breach two weeks ago, company officials said they didn’t know who was behind the attacks or where they might be based.