What is the most common explanation to the cause of the formation of "The Door to Hell" in Turkmenistan?

According to Turkmen geologist Anatoly Bushmakin, Soviet geologists initially came across the site in 1971 and believed it was rich in oil. But shortly after they began drilling, the surface and camp collapsed into a wide crater and was buried. The crater began emitting noxious gases. The geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. According to the story, over 45 years it has been burning with no end in sight.

The giant sinkhole, known more formally as the Darvaza gas crater, is an incredible 226 feet wide, 98 feet deep, and is constantly in flames. Turkmenistan has the sixth largest natural gas reserves in the world.

The crater was featured in a Die Trying episode titled "Crater of Fire". Explorer George Kourounis became the first person to ever set foot at the bottom, gathering samples of extremophile microorganisms. The episode was broadcast on the National Geographic Channel.

The years of the crater's history are uncertain. There are no official records available for any version of the events.