Some global banks briefly froze credit lines for Singapore metal traders last month after a unit of commodities giant Glencore uncovered fake warehousing receipts, people familiar with the matter said, reviving the specter of a $3 billion scandal that rocked the trading world three years ago. Two people who have metal storage dealings with Access World said the company told them the receipts were from a third party, not issued internally. "We checked with (Access World) and all our stock was in good order," said one of the people, an official at a Singapore trading house.