Feb 25 (Reuters) - U.S. Senator Chuck Grassley had

demanded detailed information on UnitedHealth's ( UNH ) Medicare

billing practices, according to a letter sent to CEO Andrew

Witty on Monday.

Shares of the company fell 1.7% to $453.90 in afternoon

trading after the Wall Street Journal first reported the news.

Over the last several months, The WSJ has run a series

of stories detailing how UnitedHealth ( UNH ) profited from using

Medicare billing rules to its favor.

The letter by Senator Grassley cited findings from the

Journal's articles and said "the apparent fraud, waste, and

abuse at issue is simply unacceptable and harms not only

Medicare beneficiaries, but also the American taxpayer".

We welcome the opportunity to share the facts with

Senator Grassley, especially given the ongoing misinformation

campaign by the WSJ, UnitedHealth ( UNH ) said in a statement.

On Friday, WSJ reported the U.S. Justice Department is

investigating UnitedHealth's ( UNH ) Medicare billing practices, while

the health insurer said it was unaware of any new probe

underway.