NEW ORLEANS (AP) - Crews are expected this week to begin drilling a relief well at the site of a natural gas well that blew wild off the Louisiana coast but eventually was choked off by sand and sediment. The federal Bureau of Safety and Environmental Enforcement said the a rig has been moved to the site, about 55 miles southwest of Grand Isle, and will drill the relief well under contract to well owner Walter Oil & Gas Co. The work to drill into and then plug the well with mud and cement is expected to take about 35 days. It blew out on July 23. Spokeswoman Eileen Angelico says a sheen from the leak is no longer visible on the surface of the Gulf of Mexico. The agency has opened an investigation into the cause.