Police in Sydney's south-west say it is only a matter of time before they arrest people over the nation's biggest seizure of pirated DVDs.

About one million pirated discs of Asian television shows and music were allegedly found in five raids in the area this morning.

The police were called on to carry out the search warrants by an investigation company hired by the copyright owners.

Jarrod Bowditch works for the investigation company and says the number of discs found is a record.

"We believe it's the largest seizure in Australia for pirated discs," he said.

"We were involved in one in Victoria earlier this year and that was about half a million, so obviously [this one] about twice the size of that one."

He said the discs were being sold out of a shop in the Cabramatta area.

"It's very profitable for the pirates, but you can imagine the copyright owners are losing millions of dollars as well because they're not being able to receive the income from their legitimate sales," he said.