(Reuters) -The U.S. Division Of Well being and Human Companies has opened an investigation into the cyberattack at UnitedHealth Group (NYSE:)’s Change Healthcare (NASDAQ:) unit that disrupted pharmacy refills and insurance coverage claims processing.

The investigation, introduced on Wednesday, is the primary authorities probe into the Feb. 21 cyberattack that has jolted the U.S. well being system because the division processes about 50% of medical claims within the nation.

The probe will concentrate on figuring out the extent of the attainable breach, and compliance by UnitedHealth and the unit with federal legislation that protects delicate affected person well being info, the HHS mentioned.

UnitedHealth mentioned it might cooperate with the investigation.

“Our speedy focus is to revive our techniques, defend knowledge and assist these whose knowledge might have been impacted,” it mentioned.

The total extent of the information breach stays unknown, and UnitedHealth has mentioned it was nonetheless investigating.

UnitedHealth has blamed the hack to the “Blackcat” gang, a infamous ransomware group that has a historical past of disruptive assaults.

In a message posted to, after which shortly deleted from their darknet website, the hackers mentioned on Feb. 21 that they stole hundreds of thousands of delicate information, together with medical insurance coverage and well being knowledge, from the corporate.