Leamington Mayor John Paterson is concerned about the future of the biggest employer in his municipality.

Heinz, the ketchup giant, has been sold for $28 billion US to an investment group headed up by billionaire Warren Buffett.

If shareholders and regulators approve the sale, the company will move from being publicly traded to privately owned.

Patterson said the news took him completely by surprise.

"We've been working really hard with our federal government trying to slow down or dissuade them from doing this packaging deregulation. We felt like we were making some headway and to wake up to this announcement [Thursday], it just seems like, wow, can they throw one more monkey wrench into the works?" Paterson said.

The Heinz plant in Leamington, Ont., the tomato capital of Canada, employs 750 full-time people and an additional 300 part-time workers during harvest.

Although he's worried, Paterson said knowing Buffett is the buyer is a bit of a relief.

"I found out that it was Warren Buffett. So that kind of steadied me a little because Mr. Buffett isn't the kind of buyer who buys stuff to break it up and throw it away to make money," Paterson said. "He buys long-term, buys quality companies and we all know that H.J. Heinz is exactly that."

"It's our kind of company," Buffett said in an interview on CNBC, noting its signature ketchup has been around for more than a century. "I've sampled it many times."

Paterson said he's tried to get information out of Heinz Canada in Toronto but has been unsuccessful.

In a statement, Heinz senior vice president of corporate and government affairs Michael Mullen said it's business as usual at Heinz operations around the world until the transaction receives shareholder and regulatory approval.

Leamington is home to the second-largest Heinz plant in the world.