May 14 (Reuters) - The U.S. Department of Justice (DOJ)

is investigating UnitedHealth Group ( UNH ) for possible

Medicare fraud, the Wall Street Journal reported on Wednesday.

While the exact nature of the criminal allegations are

unclear, the Journal said, citing people familiar with the

matter, the probe by the healthcare-fraud unit of the DOJ's

criminal division is active since at least last summer.

Reuters could not immediately confirm the details of the

report.

The company's stock fell 6.7% in after-hour trade following

the WSJ report.

In February, the Journal had reported a civil fraud

investigation by the DOJ into the company's practices for

recording diagnoses that triggered extra payments to its

Medicare Advantage plans.

A DOJ spokesman declined to comment to the Journal.

UnitedHealth Group ( UNH ) and the DOJ did not immediately respond to

Reuters requests for comments.

(Reporting by Bipasha Dey in Bengaluru; Editing by Sumana Nandy

and Arun Koyyur)