Immigration officials swooped on a Pie Face operation in Sydney on Monday following reports of the exploitation of foreign workers.

The raid was triggered by a tip-off to the Department of Immigration and Border Protection earlier this month, which included claims relating to the underpayment of a group of workers on 457 visas.

Pie Face plans to open 24 new stores in cities from the Middle East to New Zealand.

The immigration department would not discuss details of the investigation but confirmed it was aware of the allegation Pie Face workers had been underpaid.

It's understood the surprise visit on Monday was part of an integrity and compliance operation being undertaken by the Department of Immigration and it is likely accounting data including wage payments were seized.