The Commerce Commission has received nine complaints relating to coronavirus and prices.
It comes as a fourth person in New Zealand was this morning confirmed to have contracted the virus.
Meanwhile, businesses in New Zealand were free to set their own prices for products and the competition, consumer and regulatory agency said there was little it could do.
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"The Commerce Commission does not regulate retail prices," a spokesman told the Herald.
"However, the Fair Trading Act prohibits misleading and deceptive conduct and false representations, including on pricing.
"This means that if a business gives a reason for a price increase it must be true or the business risks breaching the law."
Elsewhere, the man confirmed to be infected with Covid-19 this morning by the Ministry of Health was the husband of a woman already infected.
The pair returned from a trip to Italy last week and the family, which includes children at two North Shore high schools, were in isolation.
Both schools the children attend, Westlake Boys' and Girls' high schools, had been alerted.
One of New Zealand's four patients is an NZ Steel employee, with staff told about the confirmed case via email and in emergency meetings.
The steel manufacturer's chief executive, Gretta Stephens, told staff the company had been advised of the new case on Thursday morning.
"We are pleased to advise that the affected employee has confirmed that they are not seriously ill and are in isolation at home," Stephens wrote in an email to staff.
She said the company was working with the Ministry of Health to handle the situation.