Updated

The FBI is investigating threats purportedly from the hacking collective that calls itself Anonymous to bring down the New York Stock Exchange on Monday by hacking into its computer system.

Members of the notorious hacker group appear to be threatening to bring the Occupy Wall Street protests in New York to a dangerous new level, sounding a call to “declare war on the New York Stock Exchange" on Monday by “erasing" it from the Internet.

“The FBI is aware of these schemes and threats and is looking into the matter,” FBI spokesman Tim Flannelly told FoxNews.com.

The hackers say they plan to launch a DDoS (or distributed denial of service) attack on the NYSE’s computer systems -- the same type of computer attack that brought down numerous websites last Spring, making them inaccessible.

Anonymous has also separately declared the Stock Exchange announcement a hoax, and it remains unclear whether this is an official effort by Anonymous, a group of rogue hackers or someone else entirely.

Either way, the FBI is investigating.

“It is a crime to show the intent to carry out a hack when you are in possession of software or computer applications to do so and we take it seriously,” FBI spokesman Flannelly said.

In one of the videos, which was addressed to the media, a narrator states, “We can no longer stay silent as the population is being exploited and forced to make sacrifices in the name of profit. We will show the world that we are true to our word. On October 10, NYSE shall be erased from the Internet ... expect a day that will never, ever, be forgotten.”

In a video addressed to the public, the narrator states, “We are the 99 percent. You have complained that something needs to be done. You now have an opportunity to make a difference. Join the protests. Organize your own. Watch online. Be a part of the movement.”

A digital flier has circulated online with the banner “Operation Invade Wall Street: This is not an occupation. This is an invasion,” and instructions how to participate in “three simple steps.”

It provides a link to download a program to participate as well as the URL for the Stock Exchange (www.nyse.com) and the date and time, October 10th at 3:30 p.m., to attack.

Would-be participants are also urged to “spread the F----- word.”

Still, other Anonymous representatives denied the plans.

A second letter has been posted online, also with Anonymous on the masthead, that references rumors of the planned attack and disclaims the group’s association:

“We have taken notice to a planned attack which has been named #InvadeWallStreet ...We strongly advise against this action and everything it entails to,” the letter says.

“We do not want history to repeat itself, and are sincerely worried,” the letter adds, referencing past attacks on Visa, Paypal, and Mastercard after they refused to accept transactions for payment to WikiLeaks.

Some have taken to Twitter, claiming the DDoS threat is a hoax, or even a setup.

“Smells like a trap! Don't participate,” said one tweet with the hashtag #invadewallstreet.

“HOAX: #invadewallstreet is not a valid OP. Beware of provocateurs!!!” said another posting.