The FBI has begun a preliminary inquiry based on concerns in the US Congress over a report that media mogul Rupert Murdoch's News Corp sought to hack into the phones of September 11 2001 victims, a law enforcement official said.
The decision to step in was made after Congressman Peter King and several other members of Congress wrote to FBI Director Robert Mueller demanding an investigation, said the official.
The official stressed that the review was in its infancy but declined to discuss the scope of it or say what steps had been taken.
The FBI routinely makes preliminary inquiries into issues raised by politicians and others to determine whether a full-blown investigation is needed.
US attorney general Eric Holder confirmed the early stages of an inquiry into the allegations that first surfaced in the UK.
"There have been members of Congress in the United States who have asked us to investigate those same allegations and we are progressing in that regard using the appropriate criminal law enforcement agencies in the United States," Mr Holder said at a press conference in Australia while attending a meeting of the attorneys-general of the US, United Kingdom, Canada, New Zealand and Australia.
The suggestion that September 11 victims also may have been were targeted surfaced on Monday in the Mirror. The newspaper quoted an anonymous source as saying an unidentified American investigator had rejected approaches from unidentified journalists who showed a particular interest in British victims.
Prime Minister David Cameron vowed that the claim would be investigated.
US Department of Justice spokeswoman Laura Sweeney said that the department "does not comment specifically on investigations, though anytime we see evidence of wrongdoing, we take appropriate action".
Mr King's letter had called for "an immediate investigation", saying it was an "urgent matter". Mr King, a Republican, said he had not officially been contacted by the FBI and said he wanted to reserve comment until he hears from the agency. "If they do, I'd be gratified," he said in a brief telephone interview.