A political flap over Environmental Protection Agency officials' use of "alias" emails has generated more fallout.

Last fall, GOP lawmakers blasted then-EPA Administrator Lisa Jackson for using a secondary email account. They claimed the account, under the name "Richard Windsor," was a ploy to circumvent agency transparency rules.

On Feb. 15, James Martin, the head of EPA's Denver-based Region 8, said he would resign. An EPA spokeswoman says Martin resigned for "personal reasons" and did not comment further. But some Republicans speculate that the email probe was a factor in Martin's decision. Sen. David Vitter (R-La.) said Martin probably was resigning "in part because of the open investigation about his use of a non-official email account to conduct official business." Vitter also said EPA Acting Administrator Bob Perciasepe appears to have used a similar type of email account to communicate with Jackson.

EPA says it has been standard practice for more than a decade for agency officials to have more than one account. The spokeswoman said, "The email address for the public account is posted on EPA's website and is used by hundreds of thousands of Americans to send messages to the administrator. The internal account is an everyday, working email account of the administrator to communicate with staff and other government officials."