A volcano erupted near Tokyo early Monday, spewing a plume of smoke more than a mile (1.6 kilometers) high and raining ash down on parts of the city. There were no immediate reports of injuries or damage.

Mount Asama, about 90 miles (145 kilometers) northwest of Tokyo, erupted at 1:51 am (0451 GMT) Monday, according to Japan's Meteorological Agency. Chunks of rock from the explosion were found about 3,300 feet (1,000 meters) away from the volcano.

The agency said volcanic ash fell on nearby areas as well as parts of Tokyo. TV reports showed neighborhoods sprinkled with white flakes.

An alert level of three, which urges nearby residents to take caution, was kept in place for a 2.5 mile (4 kilometer) radius. Alert level four advises residents to prepare for evacuation, while level five, the highest, orders evacuation, according to the agency.

The last major eruption of Mount Asamo took place in September 2004, the agency said.

With 108 active volcanos, Japan is among the most seismically busy countries in the world. The country lies in the "Ring of Fire" - a series of volcanoes and fault lines that outline the Pacific Ocean.

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White smoke rises from Mount Asama in Tsumagoi, about 140 km (87 miles) northwest of Tokyo, Feb. 2, 2009. The volcano in central Japan erupted on Monday, spewing hot rocks and ash, but there was no major damage in the sparsely populated vicinity, the Japan Meteorological Agency said. (Xinhua/Reuters Photo) Photo Gallery>>>

    TOKYO, Feb. 2 (Xinhua) -- Japan's Mt. Asama, straddling central Gunma and Nagano prefectures, erupted early Monday from its summit crater, sending ash showers as far as Tokyo and its vicinity in the southern Kanto region, the Japan Meteorological Agency said.

    The 2,568-meter volcano, about 145 kilometers from Tokyo, erupted at 1:51 a.m. (0451 GMT) Monday, the meteorological agency said. TV reports showed ashes showering down in neighboring regions.

White smoke rises from Mount Asama in Tsumagoi, about 140 km (87 miles) northwest of Tokyo, Feb. 2, 2009. (Xinhua/Reuters Photo) Photo Gallery>>>

    In the town of Karuizawa in Nagano Prefecture, about 2 millimeters of ash scattered in the area, but local government said it has not received any reports of damage.

    The last major eruption of the volcano happened in 2004, causing damage to local crops.

    On Sunday, the agency had raised the volcanic eruption alert level for Mt. Asama from 2 to 3 on the 5-stage warning scale. Level 3 prohibits people from going on Mt. Asama.