David Petraeus sex scandal envelops US commander in Afghanistan, Gen. John Allen

Gen. John Allen, the leading US commander in Afghanistan — and awaiting confirmation as the new NATO supreme allied commander for Europe — is now being investigated as part of the widening scandal around former CIA director David Petraeus.

US Defense Secretary Leon Panetta said Tuesday that Allen was under investigation over allegedly inappropriate communications with a Tampa social planner linked to Petreaus, Jill Kelley, the Wall Street Journal reported.

Panetta said that he had asked the Senate to put on hold Allen's confirmation as a NATO's chief in Europe.

The Guardian cited an American official as saying the FBI uncovered between 20,000 and 30,000 pages of communications – mostly emails spanning from 2010 to 2012 – between Allen and Kelley.

Kelley is a long-time friend of the Petraeus family, the Guardian added.

More from GlobalPost: The Petraeus affair: The ethics of a scandal

The official responded to a question about the possible disclosure of classified information by saying:

"We are concerned about inappropriate communications. We are not going to speculate as to what is contained in these documents."

Later on Tuesday, White House press secretary Jay Carney said President Obama had faith in Allen, according to Talking Points Memo. Carney said the president praised Allen's service in Afghanistan.

"The president thinks very highly of Gen. Allen and the service to his country," said Carney, noting that Obama has not yet spoken directly to Allen.

"He's focused on his policy agenda," Carney said of Obama, according to Politico. "He's not going to make grand pronouncements or decisions" based on the Petraeus and Allen scandals, said Carney.

"I really would ask you to not extrapolate broadly. The president has great confidence in the military, great confidence in his commanders."

Petreaus, Allen's predecessor as the top coalition commander in Kabul, resigned as CIA director last week after acknowledging an extramarital affair with his biographer, Paula Broadwell.

In a further development regarding Broadwell, FBI agents visited the writer's Charlotte, North Carolina home Monday night.

While an FBI spokeswoman declined to say what the agents were doing there, the agents brought cardboard boxes often used for evidence gathering during a search, the Associated Press reported. 

Agents also photographed the house as reporters looked on.