A company which ran a controversial cash-drop in Auckland has been fined for sending thousands of unsolicited text messages.

Greenback Ecommerce Limited, trading as The Safety Warehouse, was fined $30,000 by the Department of Internal Affairs.

The department said the business was investigated after it received complaints from the public about unsolicited commercial texts.

"These messages took advantage of the second Covid-19 outbreak to sell face masks and failed to provide an unsubscribe facility," the DIA said in a statement.

"DIA executed a search warrant on The Safety Warehouse's mobile network service provider and identified over 4800 unsolicited commercial SMS text messages sent on 12 August 2020.

"The text messages were sent to over 4700 unique mobile numbers with over 80 recipients receiving multiple texts."

The department said it was not the first time the company had faced enforcement action over unsolicited messages. It was given a formal warning earlier this year, and was sent information about compliance.

"The Safety Warehouse then further breached the Act in August and was issued a NZ$300 civil infringement notice."

DIA's manager of digital marketing and systems, Lisa Wilkin-Krug, said she hoped the penalty encouraged businesses to comply with the law.

"It is vital to obtain the recipient's consent prior to sending a commercial electronic message and to provide a functional unsubscribe facility within the message. Failure to do so can result in enforcement action by DIA."

The Safety Warehouse is also being investigated by the Commerce Commission after it hosted a $100,000 promotional cash-drop in Auckland.

Police referred the matter to the commission after some of the money turned out to be vouchers for the company's online store, printed to look like $5 notes.

The Safety Warehouse managing director Andrew Thorn said at the time that the event had been "unfairly characterised" as an event with fake money, when real funds were given away as anticipated.