The FBI has opened an investigation into allegations that News of the World journalists tried to hack the phones of victims of the 9/11 attacks in New York.

The inquiry takes the fallout from the phone-hacking scandal officially beyond the UK for the first time, wiping around $1 million off News Corp's share price last night in the US, where its media outlets include Fox News, the Wall Street Journal and the New York Post.

Shares in the New York-based company fell 3 per cent in just an hour yesterday, after the news of the FBI inquiry broke, dropping to a low of $15.50, before finishing at $15.99. News Corp shares in the US have fallen almost 11 per cent over the past week.

The launch of the FBI inquiry comes after Peter King, a New York congressman and chairman of the homeland security committee, wrote to the director of the FBI Robert Mueller to ask him to open an investigation into the 9/11 allegations.

"The 9/11 families have suffered egregiously, but unfortunately they remain vulnerable against such unjustifiable parasitic strains," wrote King.

"We can spare no effort or expense in continuing our support for them."

King warned that if the allegations were shown to be true they would "merit felony charges" and "any person found guilty should receive the harshest sanctions available under law".

Rupert Murdoch, chief executive of News Corp, and his son James were summonsed yesterday to give evidence to the culture, media and sport select committee in the UK.

They will attend alongside Rebekah Brooks, chief executive of News Corp's UK newspaper arm, News International.

News International is currently under investigation by the Metropolitan police for phone hacking and corruption. Evidence emerged last week that staff at one of the publishers' titles, the News of the World, paid police officers for information.

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