The review will include a look at whether the agent went through the proper chain of command at the FBI to raise his concerns, the official said. Humphries is still on duty in the Tampa office.

Reports by officials familiar with the e-mail messages between Kelley and Allen give conflicting impressions about their potentially inappropriate nature -- with one U.S. official saying "John Allen would be very embarrassed by them" and a senior official close to the general saying they don't point to a sexual or romantic relationship.

That Allen remains in command in Afghanistan suggests that there is no criminal issue, a U.S. official told CNN. But the official said the Defense Department's inspector general could still find evidence of criminal conduct.

The investigation into the e-mails connected to Allen and Kelley led to the discovery of the affair between Petraeus, 60, and Broadwell, 40.

The fallout has been widespread, but there are signs that the FBI investigation is winding down, said CNN contributor Tom Fuentes, a former FBI assistant director.

There is no indication of criminal activity on the part of Petraeus or that he disclosed classified information, senior federal law enforcement officials told Fuentes.

Kelleys' financial troubles

Kelley hosted top military brass at her home, but it's unclear if Allen or Petraeus were aware that her family was experiencing financial difficulties or of the unusual background of a charity they founded.

Public records show that in April 2010, about six years after the Kelleys bought their $1.5 million home, Regions Bank filed to foreclose on the property, saying the couple hadn't made a mortgage payment since September 2009.

Florida records show there are at least nine lawsuits involving money and the Kelley family, including unpaid credit card bills of more than $320,000.

Public records also show the Kelleys founded a cancer research charity in 2005 called the Doctor Kelley Cancer Foundation. In a 2008 federal tax return, the Kelleys' charity reported it spent the exact amount of money it raised:$157,000.

The charity's money paid for parties, transportation, legal bills and other administrative costs. There is no evidence any of the money was used for cancer research or caring for cancer patients.

Asked for the Kelleys' side of the story, a source close to the family told CNN the source didn't have enough information to respond.

Broadwell's security clearance

It appears unlikely that Broadwell would face prosecution in the case, a senior law enforcement official said.

Officials continued to review materials taken from her home, and the FBI needed a presumption that there were classified materials there when they obtained a search warrant. But it appears that any violations of releasing classified information appear not to be egregious.

Before the warrant was issued, FBI agents approached high-level Pentagon officials to ask them if material they had tied to Broadwell could be considered classified, two U.S. officials with direct knowledge of the case said. Defense Department officials said they were classified.

As a military reservist, Broadwell had security clearance but presumably would have no clear reason to have classified information in her home, the officials said. The military has many safeguards in place, including not allowing data to be saved on hard drives and restricting what can be sent out by e-mail, to prevent secret info from getting out.

Broadwell's security clearance with the government has since been suspended, pending the outcome of the investigation, said the officials.

Petraeus reportedly has not been following the media firestorm over the extramarital affair that led to his resignation.