A German road worker died Monday when a machine he was operating in an autobahn construction zone hit a buried object that exploded, according to German authorities and news reports.

The explosion occurred as a milling machine was cutting through the concrete road surface on A-3 near Aschaffenburg in northern Bavaria. The large machine that struck the object was blown to pieces and its operator was fatally injured, The Associated Press reported.

Autobahn 3 is a road many Americans use when traveling between Frankfurt and Würzburg. However, U.S. military police “have no reports of injuries or damages to any Americans,” said Eva Maldonado, a spokeswoman for U.S. Army Garrison Darmstadt.

German authorities initially thought the explosive device was a World War II bomb, probably dropped from an Allied plane more than 60 years ago. But German news reports quoted a police spokesman Monday as saying the explosion, while deadly, seemed too small to be a WWII bomb.

“We cannot yet say whether this was an aerial bomb or something else,” Karl-Heinz Schmitt, a spokesman for police in Würzburg, told n-tv.

Unexploded ordnance from WWII still peppers the German countryside. In the state of North Rhine-Westphalia alone, about 400 to 600 wartime bombs are found each year, according to the German news magazine Der Spiegel.

Noontime traffic in both directions on A-3 came to a standstill following the explosion as police and emergency responders arrived on the scene. Bomb specialists from Munich were flown to the scene by helicopter to assist in the investigation. The road reopened after five hours, according to police.

Police did not identify the construction worker who was killed, but a German news report said the man was from Dresden.

In addition, several vehicles on the highway were damaged by flying debris and at least five people — four construction workers and a female motorist — were treated for shock.

The Associated Press contributed to this report.

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