The US Securities and Exchange Commission is investigating the false news that appeared on CNN's iReport website at the end of last week stating Apple CEO Steve Jobs had suffered a major heart attack.

The agency's enforcement unit is trying to determine if the report was intended to push down the company's stock price, or, if it was just a prank, attributed to 4chan by some.

The story read: "Steve Jobs was rushed to the ER just a few hours ago after suffering a major heart attack", causing shares to fall as much as 5.4% almost straight away.

CNN - cooperating with the SEC's probe - removed the "entirely user-generated" new story and disabled the user's account as soon as it was brought to their attention.

Gene Munster of Piper Jaffray said that stock would plummet by a quarter if Jobs were to "leave" for any reason.