The Obama administration on Monday gave oil giant Royal Dutch Shell final permission to conduct exploratory drilling for oil and natural gas in the Arctic Ocean near Alaska.

The company began drilling last month under a temporary permit, but since it didn't have the proper emergency response vessel in the region at the time, it was only allowed to drill into the top sections of two wells off the coast of Alaska.

Now that the vessel has been repaired and is present in the area, the Bureau of Safety and Environmental Enforcement announced Monday that it issued a final permit to the company, which will allow it to drill an exploratory well into oil-bearing rock below the ocean floor in the Arctic, reported The Wall Street Journal. It's the first such drill since Shell's last exploratory well was drilled some two decades ago, according to BBC.

Experts estimate that more than 20 percent of the world's undiscovered oil and gas reserves are located in the Arctic.

The announcement angered environmental activists who say it goes against President Barack Obama's stated commitment to address climate change by moving away from fossil fuels and toward more renewable energy. They say the oil should be left alone, as it's only a matter of time before a spill devastates the region's ecosystem, as seen in the Gulf of Mexico in 2010. Some say the machinery used in drilling also has the potential to disturb wildlife in the area, according to the LA Times.

"To preserve his climate legacy, President Obama must change the course on Arctic drilling set eight years ago by former President George W. Bush, and not perpetuate it," said Michael Brune, executive director of the Sierra Club. "Granting Shell the permit to drill in the Arctic was the wrong decision, and this fight is far from over. The people will continue to call on President Obama to protect the Arctic and our environment."

But the U.S. government insists it is monitoring Shell's activities "around the clock" to ensure the "utmost safety," according to BBC.

"Activities conducted offshore Alaska are being held to the highest safety, environmental protection, and emergency response standards," Brian Salerno, director of the Bureau of Safety and Environmental Enforcement, said in a statement, reported AFP.

A Shell spokesman stressed that the company is focused on safety. "We remain committed to operating in a safe, environmentally responsible manner and look forward to evaluating what could potentially become a national energy resource base," spokesman Curtis Smith said, reported BBC. "It's possible we will complete a well this summer but we're not attaching a timeline to the number of feet drilled. Safe, efficient operations will ultimately determine the progress we make."

If Shell discovers oil or natural gas, it must then apply for additional permits to extract the oil, which the Wall Street Journal says could take a decade or more. Shell has not yet found any oil or natural gas since it started drilling in 2007. Bad weather and mechanical failures that botched a drilling attempt in 2012 resulted in tighter restrictions.

The company has already committed about $7 billion to the effort and plans to invest more than $1 billion more in the project this year. The company has until late September to drill before ice makes it too difficult to drill, according to Smith.