ANCHORAGE, Alaska — One of two drill ships used by Royal Dutch Shell PLC for Arctic drilling off Alaska's coast is under investigation for problems with crew safety and pollution control equipment, the Coast Guard said today. The Noble Discoverer, owned by Noble Corp., was ordered for more than two weeks to remain in port in Seward while deficiencies were addressed. The Coast Guard has cleared the vessel to leave for a shipyard in the Pacific Northwest and it likely will begin the trip under tow before the weekend, Shell Alaska spokesman Curtis Smith said. A Noble Corp. spokesman didn't immediately answer a phone call today, but a statement issued by the company said it is working cooperatively and diligently to rectify deficiencies and maintenance issues raised by the Coast Guard. Smith said Shell takes the inspection seriously. "The Noble Discoverer will not deploy to Alaska next season until all of the issues have been corrected," Smith said.