HARRISBURG - State Treasurer Rob McCord said he was stepping down after six years in office, as signs emerged that he might be under scrutiny by federal authorities.

Investigators have been asking questions about McCord's campaign-related actions in recent months, according to several sources close to the examination.

The extent of their inquiry was unclear.

McCord, who submitted his resignation letter to Gov. Wolf Thursday morning, could not immediately be reached for comment. His resignation comes half-way into his second term.

His spokesman, Gary Tuma, also could not be reached.

In 2014, McCord, a former venture capitalist from Bryn Mawr, made a failed bid for governor, losing to Wolf in the Democratic primary.

In his resignation letter to Wolf, McCord said he felt he accomplished what he set out to do - modernizing the agency, making it more efficient and expanding its role as a fiscal watchdog - and would resign effective Feb. 12 to return to the private sector.

"It has been the privilege of a lifetime to serve the citizens of Pennsylvania as their elected State Treasurer for the past six years," McCord said in his letter. "But with my goals at Treasury now achieved - and with a new governor now in office to appoint my successor-it is time for me to return to the private sector."

McCord named the agency's chief counsel, Christopher Craig, to serve as acting Treasurer.

The governor nominates a successor who must be confirmed by the Senate.

Among the accomplishments cited in the letter, McCord said he eliminated a $400 million unfunded liability within the state's College Tuition Account Guaranteed Savings Program, significantly expanded the abandoned property program within the agency, returning more property to its rightful owners, created a short term lending initiative within the Capital fund saving millions and improved transparency within the tax appeals process.

In a statement, Wolf praised McCord's service.

"In the past six years, Treasurer McCord has saved our commonwealth over a billion dollars by modernizing the Treasury Department, expanding innovative programs for our citizens, and protecting Pennsylvania's best interests. I thank him for his tremendous service, commitment and dedication and wish him well in his new endeavors."