Prosecutors say they have unearthed evidence in recent international money-transfer investigations that Chinese banks may have flouted United States sanctions against Iran.

Now, as they investigate global banks suspected of funneling billions of dollars through their American branches to Iran and other sanctioned nations, the prosecutors are looking for transactions that could offer more information on the banks’ dealings with Iran.

Information on how Chinese banks may have routed money on behalf of Iranian banks and corporations is more valuable than any monetary settlement the authorities could win from the global banks, law enforcement officials with knowledge of the cases said, because the United States could use the information to strengthen its efforts to choke off economic dealings with Iran.

The United States has been ratcheting up its sanctions as Iran’s nuclear ambitions raise the risk of military action from Israel and shocks to the global economy. The investigations of two London-based banks, HSBC and Standard Chartered, could prove especially fruitful, said the law enforcement officials, who declined to be identified because the cases are continuing.