In its quarterly report filed with the U.S. Securities and Exchange Commission, Omaha, Nebraska-based Berkshire said it alerted federal authorities including the Department of the Treasury on Friday about the transactions in question.

It said the customers "include or may include parties that meet the definition of the 'Government of Iran.'"

The transactions took place from June 2013 to November 2015, and generated about $2,500 of profit on $45,000 of revenue, Berkshire said.

Berkshire did not identify the unit involved or when it learned there might be a problem, but said the unit has stopped shipments to the Iran parties and does not intend to resume them.

It also said it has hired outside lawyers to help it conduct an internal probe, and will cooperate with government agencies.

Berkshire has close to 90 operating units, mostly in the United States. It did not immediately respond to requests for additional comment.

In August 2012, President Barack Obama signed into law the Iran Threat Reduction and Syria Human Rights Act, which makes U.S. companies liable for various activities related to Iran, including support for terrorism and human rights abuses, according to the U.S. Department of State.

The law also requires Berkshire and other companies that make periodic SEC filings to disclose various dealings with Iran.

Berkshire also disclosed first-quarter results on Friday.