The US trade regulator has launched a probe into "grey market" imports of energy drinks that Monster Beverage Co. claims have infringed its trademarks.

The US International Trade Commission (USITC) has issued a formal notice of investigation after Monster filed a complaint against the shipment of products into the country.

The investigation names a total of 13 respondents.

Monster said the imports bear its trademarks despite being made and packaged for sale “solely outside the US”. It is seeking cease and desist orders against the respondents.

The matter will now proceed before an administrative law judge.

“Extensions of time for submitting responses to the complaint and the notice of investigation will not be granted unless good cause therefor is shown,” the USITC said.

Failure to respond timely to the allegations will waive the right to contest them and may result in exclusion or cease-and-desist orders, added the agency.

In the opening three months of the year, Monster booked a 26.9% rise in first-quarter net sales to $2.35bn, contributing to 28% increases in operating income and net income. Adjusted for exchange rates, the US energy-drinks company’s sales grew 22.1%.

The company reported rising sales at home and abroad. In the US, sales grew 16%. In Monster’s international markets, sales increased 33%, or by almost 45% when including the impact of foreign exchange.

CEO Hilton Schlosberg said Monster had “an incredible quarter”.

He added: “Net sales crossed the $2bn threshold for the first time in the company’s history for a fiscal first quarter.

“Our net sales to customers outside the US increased 44.9% in the 2026 first quarter to approximately 45% of total net sales. This represents the highest percentage of net sales to customers outside the US recorded by the company to date for a single quarter.”