The Financial Markets Authority is investigating suspect trading in Xero shares that preceded a major capital raising by the software firm earlier this year.
An NZX spokeswoman today confirmed the sharemarket operator had referred the matter to the FMA on June 8.
"Much of the trading activity during the relevant period was undertaken offshore, which impacted NZX Surveillance's review process and the ultimate timing of the referral," she said.
"The FMA continues to consider the matter and is the most appropriate to contact for any further enquiries."
An FMA spokeswoman said the regulator could not comment until its inquiry into Xero was completed.