AlHijjah 3, 1435, Sep 27, 2014, SPA -- A volcano in central Japan erupted in spectacular fashion on Saturday, catching mountain climbers by surprise and injuring at least 11 people, including seven who lost consciousness, according to AP. With a sound likened to thunder, Mount Ontake erupted shortly before noon on a clear autumn day, spewing large white plumes of ash high into the sky and sending people on the mountainside fleeing. The eruption continued into the night, blanketing the surrounding area in ash. More than 250 people were stuck on the slopes for hours, many taking refuge in mountain lodges that dot the way up. By evening, most had made or were making their way down, though some decided to spend the night. Some with injuries didn't want to risk coming down the ash-covered paths. As of late afternoon, eleven people had been reported injured, eight seriously, including the seven who lost consciousness, said Nagano prefecture crisis management official Minoru Kashiwabara. There was no update on the status of the injured early Saturday evening. One witness told Japanese public broadcaster NHK that the eruption started with large booms that sounded like thunder. In a YouTube video, shocked climbers can be seen moving quickly away from the peak as an expanding plume of ash emerges above and then engulfs them. Many of those who made it down emerged with clothes and backpacks covered in ash. They reported being engulfed in total darkness for several minutes. Mikio Oguro, an NHK journalist who was on the slope on an unrelated assignment, told the station that he saw massive smoke coming out of the crater, blocking sunlight and reducing visibility to zero. "Massive ash suddenly fell and the entire area was totally covered with ash," he said by phone. He and his crew had to use headlamps to find a lodge. "My colleagues later told me that they thought they might die," Oguro said. Two Jetstar flights headed to Tokyo's Narita International Airport diverted to Kansai International Airport in western Japan as a precaution. Japan's meteorological agency raised the alert level for Mount Ontake to 3 on a scale of 1 to 5. It warned people to stay away from the mountain, saying ash and other debris could fall up to 4 kilometers (2.5 miles) away. The 3,067-meter (10,062-foot) Mount Ontake sits on the border of Nagano and Gifu prefectures, on the main Japanese island of Honshu. The volcano's last major eruption was in 1979.