ANCHORAGE, Alaska — Calls for federal scrutiny of Royal Dutch Shell PLC drilling operations in Arctic waters swelled Thursday with a request for a formal investigation by members of Congress.

The House Sustainable Energy and Environment Coalition called on the Interior Department and the Coast Guard to jointly investigate the New Year’s Eve grounding of the Shell drilling vessel Kulluk on a remote Gulf of Alaska island, and a previous incident connected to Arctic offshore drilling operations in 2012.

The coalition is made up of 45 House Democrats.

“The recent grounding of Shell’s Kulluk oil rig amplifies the risks of drilling in the Arctic,” they said in a joint statement. “This is the latest in a series of alarming blunders, including the near-grounding of another of Shell’s Arctic drilling rigs, the 47-year-old Noble Discoverer, in Dutch Harbor and the failure of its blowout containment dome, the Arctic Challenger, in lake-like conditions.”

The coalition believes these “serious incidents” warrant thorough investigation, the statement said.

Shell Alaska spokesman Curtis Smith said in an email that the company is in full support of, and is providing resources for, the investigation of the grounding by the Unified Incident Command, made up of federal, state and company representatives. Smith said the findings will be available to the public.

Shell incident commander Sean Churchfield said at an Anchorage news conference later Thursday that two more salvage crews had boarded the vessel and found damage to emergency and service generators, and to the Kulluk’s upper deck.

The vessel is upright and stable, and the Coast Guard has said there is no indication of a fuel leak.

“Findings include some wave damage to the top sides of the vessel, and a number of watertight hatches have been breached, causing water damage inside,” Churchfield said. The team has secured some of the open hatches, he said.

Damage to the generators means salvagers may have to bring external generators on board or work without power, Churchfield said. He confirmed salvagers heard “breathing” from a vent but said they couldn’t immediately determine whether it was a breech or natural venting.

Salvage is in the assessment stage, Churchfield noted, and options are being developed. He wouldn’t speculate on whether the Kulluk is seaworthy or when it might be moved.

An emergency towing system was deposited on deck, and spill response equipment has been staged.

“I want to reiterate there is no limitation on resources, personnel or equipment being deployed as part of the response and recovery activities,” Churchfield said.

Coast Guard Capt. Paul Mehler said the top concern remains the safety of responders working in what continues to be hazardous flying and marine conditions.

The Kulluk is a non-propelled, 266-foot diameter barge with a reinforced funnel-shaped hull designed to operate in ice. It is carrying more than 140,000 gallons of diesel and about 12,000 gallons of lube oil and hydraulic fluid. Centered on the vessel is a 160-foot derrick. It drilled during the short open-water season in the Beaufort Sea.

A 360-foot anchor handler, the Aiviq, was towing the Kulluk from Dutch Harbor to Seattle last week for maintenance and upgrades when the tow line snapped south of Kodiak. Lines were reattached at least four times but could not be maintained. A lone tugboat still attached Monday night in a vicious storm couldn’t control the vessel and cut it loose as it neared land.

After the grounding, critics quickly asserted it has foreshadowed what will happen north of the Bering Strait if drilling is allowed.

Environmentalists for years have said conditions are too harsh and the stakes too high to allow industrial development in the Arctic, where drilling sites are 1,000 miles or more from the closest Coast Guard base.

Two national organizations kept up the drumbeat Thursday by calling for a halt to all permitting for Arctic offshore drilling in the wake of the grounding.

“This string of mishaps by Shell makes it crystal clear that we are not ready to drill in the Arctic,” said Chuck Clusen of the Natural Resources Defense Council. “Shell is not Arctic-ready. We have lost all faith in Shell, and they certainly don’t have any credibility left.”

Lois Epstein, a civil engineer who works for The Wilderness Society in Anchorage, said Shell has made troubling, non-precautionary decisions that put workers and the Coast Guard at risk.

“These ongoing technical and decision-making problems and their enormous associated costs and risks taken by our military personnel once there were problems should lead the federal government to reassess its previous permitting decisions regarding Shell,” Epstein said.

In the short term, she said, damage to the Kulluk may prevent it from being ready for the 2013 open water season. Besides drilling in the Beaufort, the barge was supposed to be on hand for drilling a relief well if Shell’s drill vessel in the Chukchi Sea, the Noble Discoverer, experienced a wellhead blowout and was damaged, Epstein said.

Shell has maintained it has taken a heads-up approach to anticipating and reacting to problems.

Shell Alaska spokesman Smith said Wednesday the Kulluk had been towed more than 4,000 miles and had previously experienced similar storm conditions. Shell staged additional towing vessels along the route in case there were problems, he said.

“We know how to work in regions like this,” Smith said. “Having said that, when flawless execution does not happen, you learn from it, and we will.”