A giant hole that was spotted by a helicopter flying over northern Siberia continues to perplex scientists.

According to the Siberian Times, the hole is 80 meters (260 feet) wide and has an unknown depth. It is located in the Yamal Peninsula in the Arctic Ocean.

A team of Russian scientists has been sent out to investigate the formation. But an Australian scientist told the Sydney Morning Herald that the large opening probably is the result of an ice formation that has melted.

“Certainly from the images I’ve seen, it looks like a periglacial feature, perhaps a collapsed pingo,” said Dr. Chris Fogwill, a polar scientist at the University of New South Wales.

According to Fogwill, pingos are blocks of ice that are formed on hills of the frozen Arctic landscape. At times, they push through the earth, and when they melt they can leave a large crater. “This is obviously a very extreme version of that, and if there’s been any interaction with the gas in the area, that is a question that could only be answered by going there,” Fogwill said.

The hole was reportedly filmed from a helicopter by a Russian engineer. That video has since gone viral online.