A box some thought was a bomb created a scare in Ichikawa, Chiba Prefecture, late Saturday but was later found to be a device used for dialysis.
The 70 cm by 50 cm by 20 cm box was found on a street in the city, prompting a mobile police unit to be called in.
Just after midnight, officers in protective gear used an X-ray scanner to probe it and determined it was not explosive.
Police said the package, which had tubes and a liquid inside, also had what looked like a power cord, switch, lamp and fuse on top. It was found by a passer-by near a store about 600 meters east of Myoden subway station.