(Reuters) – Sandwich chain Subway is exploring a sale of its business, a source told Reuters on Wednesday. The sale could value the sandwich chain at more than $10 billion, the Wall Street Journal first reported. The process, which is at an early stage, is expected to attract potential corporate buyers and private-equity firms, the report said, adding that it is possible there won’t be a sale or other deal. “As a privately held company, we don’t comment on ownership structure and business plans,” a company spokesperson told Reuters in an emailed statement. Subway, one of the world’s largest qu…