The Securities and Exchange Board of India (Sebi) is probing at least three large global banks and many Indian companies for alleged round-tripping of funds by way of multi-layered transactions. The capital market watchdog, which has been looking into the matter since late 2013, has issued showcause notices to companies, sources said. Swiss banking majors UBS and Credit Suisse as well as British financial services giant HSBC are also believed to have come under Sebi's scanner, they added. A senior official declined to identify the entities being probed, saying it could come in the way of investigations.