The sex scandal that led to the resignation of CIA director David Petraeus has widened, with the top US commander in Afghanistan under investigation for alleged "inappropriate communications" with a woman who is said to have received threatening emails from General Petraeus' former lover.
Defence Secretary Leon Panetta revealed that the Pentagon had begun an internal investigation into thousands of pages of emails from General John Allen to a second woman involved in the Petraeus case.
Gen Allen succeeded Gen Petraeus as the top American commander in Afghanistan in July 2011, and his nomination to become the next commander of the US European Command and the commander of Nato forces in Europe has been put on hold.
In a White House statement, National Security spokesman Tommy Vietor said President Barack Obama has held Gen Allen's nomination at Mr Panetta's request. Mr Obama, the statement said, "remains focused on fully supporting our extraordinary troops and coalition partners in Afghanistan, who Gen Allen continues to lead as he has so ably done for over a year".
Meanwhile, FBI agents prepared a timeline of the Petraeus affair and searched the home of Paula Broadwell, the 40-year-old biographer with whom 60-year-old Gen Petraeus had an affair that led to his abrupt resignation last week.
The resignation and his acknowledgement of an affair stunned Washington because of the former general's highly disciplined and well-praised career, which had led some to speculate whether a run for the White House would be in his future. The retired army general headed US military operations in Iraq and Afghanistan before taking charge of the CIA.
It was Ms Broadwell's alleged threatening emails to Jill Kelley, a 37-year-old Florida woman who is a Petraeus family friend, that led to the FBI's discovery of communications between Ms Broadwell and Gen Petraeus indicating they were having an affair.
A Pentagon official said 20,000 to 30,000 pages of emails and other documents from Gen Allen's communications with Ms Kelley between 2010 and 2012 are under review. He would not say whether they involved sexual matters or whether they are thought to include unauthorised disclosures of classified information. He said he did not know whether Gen Petraeus is mentioned in the emails. Gen Allen has denied any wrongdoing.
According to two federal law enforcement officials, the FBI initially began a criminal investigation of unsigned, harassing emails that were sent, beginning last May, to Ms Kelley. She and her husband, Scott, were long-time friends of Gen Petraeus and his wife, Holly. FBI agents traced the alleged cyber harassment to Ms Broadwell and discovered she was exchanging intimate messages with a private Gmail account. Further investigation revealed that account belonged to Gen Petraeus, under an alias.
Agents later told Gen Petraeus that Ms Broadwell sent emails warning Ms Kelley to stay away from the general and carrying a threatening tone. Friends and former staff members of Gen Petraeus told The Associated Press that he has assured them his relationship with Ms Kelley was platonic. They said Gen Petraeus was shocked to learn last summer of Ms Broadwell's emails to Ms Kelley. Gen Petraeus also denied to these associates that he had given Ms Broadwell any sensitive military information.