The Safety Warehouse may have to fork out four times the amount of cash it promised to throw out to punters

The company advertised a 100-thousand-dollar cash drop in Auckland on Saturday -- but the crowd grew angry after discovering vouchers that looked like five dollar notes.

An investigation by the Commerce Commission will look into whether the Fair Trading Act was breached.

Consumer New Zealand chief executive Jon Duffy says if prosecuted, the Commission won't accept vouchers.

He says the penalty could be upwards of 200 thousand dollars, maybe even 400 thousand depending on the judge.