Vietnam's military is investigating the appearance of three mysterious metal balls — believed to be debris from space — which landed in the country's remote north, a senior army official said Friday. Two metal balls were discovered in northwestern Yen Bai province on January 2, army spokesman Lieutenant General Vo Van Tuan told AFP.
Later a larger ball weighing some 45 kilograms (100 pounds) landed in a maize field in neighboring Tuyen Quang province, he said.
"We are still identifying where they came from," he said, adding the army had determined they did not contain explosives or hazardous material.
The metal balls fell from the sky, he said, scaring local residents.
"Before and after these objects were discovered, the Vietnamese army was not conducting any military activity in the region," Tuan said.
Witnesses told state-run media that they heard what sounded like thunder before the balls plunged to the earth.
The Ministry of Defense has pledged to release the findings of the probe.
Strange spheres like this have previously fallen in other places around the world. Most recently, some were reported in Spain and Turkey in November.
Thanh Nien newspaper said that the initial investigation suggested the objects could have been made in Russia and come from missiles or spaceships.
Nguyen Khoa Son, a professor from the Vietnamese Space Science and Technology Program, told the VietnamNet news site that the balls might be the result of a failed satellite launch.
He said the balls did not appear to be damaged and could have fallen from an altitude of less than 100 kilometers (62 miles).
Bits of space junk fall from the sky intermittently as an estimated 500,000 pieces of debris continues to clutter the area of "near space" around the Earth. Although space is vast and mostly empty, the "near space" immediately surrounding Earth is increasingly crowded. NASA tracks roughly 20,000 pieces of old or broken debris larger than a softball from satellites and missions past.