As a part of widening investigations of the industry, California Attorney General Jerry Brown subpoenaed records related to finances and other documents from the state's seven largest health insurance companies on Thursday.

According to Brown, there were reports of illegal practices taking place among state health insurers. It was a major concern that premiums were being raised unjustly and payment of legitimate claims was being denied.

Brown would be officially launching a campaign for governor in the coming few weeks and this decision is being taken seeing the sharp rate hikes being planned by several California insurers that has also drawn national consideration.

It was said by Anthem Blue Cross, California's biggest for-profit health insurer, that premiums for some individuals will go up to 39 per cent and that when Obama administration was against it.

On Thursday, the White House and congressional Democrats for revamping the health-care system, the subject of a bipartisan policy summit in Washington, seized Anthem’s proposed rate hike.

President Barack Obama on Monday had announced new regulation of health insurers being an important part of the overhaul plan.

"Our best attorneys are going to get to the bottom of this, and where we find violations of California's unfair business laws, we intend to stop them," he said.