California Attorney General Jerry Brown subpoenaed financial records from the state's seven largest health insurance companies Thursday, saying he's concerned companies are unjustly raising premiums.

The subpoenas include Anthem Blue Cross, the state's largest for-profit health insurer, which has come under fire recently for a proposed rate hike of up to 39 percent.

"Not only are the rate increases devastating to Californians strapped by the economy, but in some cases, they are possibly illegal," Brown said in a statement.

Brown said he's also worried that the companies have been denying payment for legitimate insurance claims.

The subpoenas cover fee-for-service health plans that reimburse doctors and hospitals for each service performed. Last month, Brown's office issued subpoenas to the same seven companies regarding their managed care plans, known as HMOs.

Brown said the companies had 30 days to hand over the requested documents. He said his investigation will examine whether such increases violate state law and whether the other health plans are planning similar premium hikes.

Brown's latest move comes on the heels of state Insurance Commissioner Steve Poizner's announcement Monday that his office had uncovered more than 700 policy handling violations by Anthem between 2006 and 2009. The alleged violations include late payment of claims, providing misleading information to consumers and failing to cooperate with regulators.

Poizner, a Republican, is running for governor this year. He could face off against Brown, who is expected to announce his bid for the Democratic nomination soon.

Anthem spokeswoman Peggy Hinz declined to comment on Brown's investigation Thursday, saying the company hadn't yet received a subpoena.

Spokesmen for two of the other insurers, CIGNA and Health Net, also said they had not received subpoenas and declined to comment.

Edwin Garcia, a spokesman for Kaiser Permanente, said the company had not received a subpoena but intends to cooperate fully with any investigation.

Representatives from the remaining companies — Aetna Health, Blue Shield of California and PacifiCare — did not immediately respond to requests for comment from The Associated Press.