An office clerk in Nanao said he first noticed the anomaly when he heard a dull thud in a parking lot last week, news reports said. Looking around, he saw about 100 dead amphibians splattered on car windshields and the ground.

More reports followed from bewildered residents in Nanao.

"People speculate that a waterspout picked them up and dropped them from the air," an official at a local weather observatory told AFP. "But from a meteorological point of view, I have to say it is most unlikely."

"We have checked the weather conditions of last week, thinking gusts of wind might have hit the area but confirmed no damage," he said. "To be honest, I don't think it was anything caused by a weather condition."

Similar events -- in what is sometimes called the "Fafrotskies" phenomenon, short for "fall from the sky" -- have been reported around the world, with whirlwinds passing over water bodies and picking up frogs, jellyfish or other unfortunate animals before dumping them back to earth.

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