March 27 (Reuters) - U.S. insurer UnitedHealth Group ( UNH )

on Wednesday said it has advanced more than $3.3 billion

so far to care providers impacted by a cyberattack last month on

insurance claims system Change Healthcare.

UnitedHealth ( UNH ) said it has paid more than 40% of that total to

so-called safety net hospitals and federally qualified health

centers serving high-risk patients and communities.

Change Healthcare is a system for making and clearing

insurance claims, processing about 50% of medical claims for

around 900,000 physicians, 33,000 pharmacies, 5,500 hospitals

and 600 laboratories.

It was attacked on Feb. 21 by a hacking group calling itself

"ALPHV" - also known as "BlackCat" - causing a cash crunch at

small healthcare providers along with disruption from which the

largest U.S. health insurer could take months to fully recover.

The Department of Health and Human Services is investigating

whether there was a breach of protected health data. The State

Department has offered up to $10 million for information on the

hacking group.