Sydney auction yard fire destroys 100 cars

A blaze that destroyed more than 100 cars at the Pickles Auctions car yard in Sydney's west is no longer being treated as suspicious.

The blaze in Milperra also damaged a large number of cars.

"These cars were in stacks three high. They've lost about 100 cars that have been totally destroyed and another 100 damaged by radiant heat," NSW Fire and Rescue Superintendent Tom Cooper told AAP.

Thick black smoke alerted nearby residents to the blaze, prompting a number of calls to 000 just before 6am.

Firefighters initially struggled to gain access to the property on Nancy Ellis Leebold Drive, using a power saw to get through a security gate.

Angela Conn from Pickles Auctions said 105 cars had been confirmed destroyed in the blaze.

"The cars that were affected were salvage vehicles so they were already damaged," she told AAP.

"We'll be in contact now with the vendors who we were going to sell the cars on behalf of and let them know what has happened."

The fire was confined to a small section of the yard and the business will continue to operate as usual, she said.