"Possibly, they had been in and seen it and come back."
Mrs O'Brien believes some car batteries, worth between $6 and $12 each, were also taken.
An inspection of the property revealed the man had gained entry by cutting a hole through a fence.
The yard has security measures in place, but it was not the first time it had been burgled.
Although the burglary would not have a major financial impact on the business, Mrs O'Brien said it still affected her.
"It's not actually the scrap, it's the invasion of our privacy," she said.
"It was a locked yard. He shouldn't have been here."
Wairarapa police Senior Sergeant Carolyn Watson said police were seeking the man, who was driving a late model Holden ute.