The Commerce Commission has begun using its powers to compel people to give up information for its inquiry into alleged blackmail and extortion by supermarket giant Countdown.
A commission spokesman said it had issued notices to "a number of parties" which required them to co-operate with the inquiry.
The "section 98" notices were similar to a subpoena and anyone who failed to comply risked a fine of up to $30,000.
The spokesman said it was common practice for a commission investigation. He would not reveal who the notices had been sent to.
Food and Grocery Council head Katherine Rich said it appeared the commission was casting its net widely, because she knew of small, large, local and overseas companies who had received the notices last week.