Wells Fargo & Co's chief financial officer will retire after taking nearly a half year of unpaid leave and will be replaced by the bank's administrative chief.

The San Francisco-based bank's shares were down 2 percent to $33.40 in after-hours trading. The shares rose 2.3 percent on Tuesday before the announcement.

CFO Howard Atkins, 60, will retire in August after an unpaid leave of absence, the bank said on Tuesday. The unpaid leave begins immediately and Atkins is now replaced by Timothy Sloan, 50.

Atkins, who had been with Wells Fargo since 2001, is retiring for personal reasons, the bank said.

Analysts said the structure of Atkins' retirement raises questions about his departure.

I would think if somebody had a health issue you would have some paid time, though every company is different. It's odd, said Chris Marinac, a bank analyst at FIG Partners LLC in Atlanta.

A Wells Fargo spokesman declined to comment on the reasons behind Atkins' departure, but said the August retirement allows certain retirement benefits to vest.

Sloan was named chief administrative officer last year after previously working as head of Wells Fargo's commercial banking, real estate and specialized financial services.

Sloan joined Wells Fargo in 1987.

In turn, Patricia Callahan will take Sloan's old post. Callahan currently oversees the integration of Wachovia's operations into Wells Fargo.

(Reporting by Joe Rauch; editing by Steve Orlofsky, Andre Grenon and Matthew Lewis)