New York state’s top insurance regulator has sent subpoenas to four U.S. insurance companies as part of a probe of potential sanctions violations involving Iran, a person familiar with the matter said on Tuesday.

The Department of Financial Services sent the subpoenas to Chubb Corp, CNA Financial, Liberty Mutual and Navigators Group, demanding information related to their dealings with Swiss-based commodities giant Glencore Xstrata and its Iranian metals trade.

Glencore said last year that it had done nothing wrong when it engaged in metal swaps with Iran.

The latest subpoenas were first reported by the Wall Street Journal.

“We are in the process of complying with the subpoena. Our policies contain trade sanction exclusions that bar coverage for prohibited exposures under applicable sanctions laws,” a Chubb spokesman said to Reuters.

CNA spokeswoman Jennifer Martinez told Reuters: “We have been cooperating with the department’s investigation. CNA has a very robust compliance program and we are confident that we followed the law.”

Calls and emails to Liberty Mutual and Navigators Group were not immediately returned.

The Department of Financial Services had previously sought information from foreign insurers as part of its probe of possible sanctions violations.

The United States and other Western nations and the United Nations have imposed crippling economic sanctions on Iran on suspicions the country is seeking to develop nuclear weapons.

(Additional reporting by Luciana Lopez; Editing by Ken Wills)