New York's top legal officer has sent subpoenas to nine leading life insurers seeking information about their practices in identifying and paying out policies for deceased customers, according to a person familiar with the matter.

New York Attorney General Eric Schneiderman last month sent subpoenas to units of AXA SA, Genworth Financial Inc, Guardian Life Insurance Co of America, Manulife Financial Corp, Massachusetts Mutual Life Insurance Co, MetLife Inc, New York Life Insurance Co, Prudential Financial Inc, and TIAA-CREF, the source said.

This person requested anonymity because the probe is not public.

The Wall Street Journal first reported the life insurance investigation.

The investigation is looking into whether insurance companies have done enough to identify beneficiaries of life insurance policies once a customer dies, the source told Reuters on Tuesday.

Schneiderman's office is also seeking information about unclaimed policy proceeds that are supposed to be turned over to the state.

A spokesman for Guardian told Reuters that it is reviewing the subpoena and intends to cooperate fully with the Attorney general.

We believe our processes are compliant with all relevant regulations and serve the best interests of our participants, said a spokesman for TIAA-CREF. We're aware of this industry matter and will fully cooperate with any official requests for information.

A Genworth spokesman told the Journal that the company believes it has compliant and robust practices to determine when claim payments are due and owing, and to adhere to state unclaimed property requirements and regulations.

AXA told the newspaper it would cooperate fully with Schneiderman as well as with other states conducting similar reviews.

None of the other companies could immediately be reached for a comment by Reuters.

Also on Tuesday, New York State Insurance Department said that all life insurers licensed to do business in the state must begin using an official government death list to identify when policyholders have died and death benefits are due to their beneficiaries.

(Additional reporting by Sakthi Prasad and Renju Jose; Editing by Tim Dobbyn)