U.S. prosecutors are investigating whether Indian billionaire Gautam Adani's companies imported Iranian liquefied petroleum gas into India through their Mundra port, the Wall Street Journal reported on Monday.

A WSJ investigation found tankers traveling between Mundra in the western Indian state of Gujarat and the Persian Gulf exhibited traits experts say are common for ships evading sanctions, the report said.

The U.S. Justice Department is reviewing activities of several LPG tankers used to ship cargoes to Adani Enterprises, the WSJ said, citing people familiar with the matter.

Reuters could not immediately confirm the report.

"Adani categorically denies any deliberate engagement in sanctions evasion or trade involving Iranian-origin LPG," a company spokesman told the WSJ in a statement. "Further, we are not aware of any investigation by U.S. authorities on this subject."

Adani, the U.S. Department of Justice and the U.S. Attorney's Office in Brooklyn did not immediately respond to Reuters request for comment.

U.S. President Donald Trump said in May that all purchases of Iranian oil or petrochemical products must stop and any country or person buying any from the country would be immediately subject to secondary sanctions.

Any inquiry into Adani would come months after U.S. authorities indicted Adani and his nephew, Sagar Adani, alleging they paid bribes to secure power supply contracts, and misled U.S. investors during fund-raising in the United States.

Adani Group has called the accusations "baseless" and vowed to seek "all possible legal recourse".