Exploration drilling began this week for a record-length oil well planned by Eni that targets a formation beneath federal waters of the U.S. Arctic Ocean, regulators said Wednesday.

Eni U.S. Operating, an Italian multinational in a partnership with Shell, plans to drill the well from a man-made island in shallow state waters near Alaska's North Slope shore.

The well is expected to extend 6.5 miles into rocks beneath federal waters of the Beaufort Sea. ConocoPhillips last year announced it had set a long-distance drilling record in Alaska with a 5-mile well at its CD5 field.

Inspectors from the Bureau of Safety and Environmental Enforcement were on hand Monday, Christmas Day, to oversee compliance as operations began, the agency said in a statement.

Joe Balash, an Alaskan and a new top official in the Interior Department, said in the statement that the Arctic is important to the Trump administration's national energy strategy.

If exploration leads to development, oil production at Spy Island could increase by 20,000 barrels daily, Eni has said. North Slope oil production in November averaged 545,000 barrels daily. The island is about 15 miles northwest of Prudhoe Bay.

The drilling has drawn criticism from conservation groups concerned about increasing industrial activity in the remote and sensitive Arctic environment.

The federal agency stressed its oversight role on Wednesday. BSEE approved the drilling permit in late November. It held a pre-drilling inspection Dec. 6-10 to review equipment, procedures and safety and environmental protections.

The agency said its inspectors will visit the site as drilling continues in the coming weeks, including during critical periods such as testing of the blowout preventer designed to prevent an oil spill. The drilling is expected to last more than two months.