It’s not everyday that a Styrofoam box floats from the heavens onto a busy urban street, but that was the scene Monday on Redwood Road in Castro Valley, California. Given that the mysterious object had exposed wires and “dangerous” written on it, the bomb squad summoned by Alameda County Sheriff’s Office decided to evacuate the area and blow up the box.
Shortly after it was detonated, the object was identified as an “ozonesonde,” a harmless ozone-measuring device launched on a balloon by San Jose State University students as part of their curriculum.
Priced at about $1,000 each, an ozonesonde can reach an altitude of 22 miles (35 kilometers) before the balloon pops and a parachute deploys to guide it safely to the ground. A typical unit contains an ozone sensor, telemetry system, and a Teflon air pump. The pump was generating humming sounds noted by the bomb squad, and was also hooked up to the instrument by the visible wires.
Follow-up investigations of the exploded ozonesonde found that the label had read “not dangerous.” Sergeant Ray Kelly said the bomb squad’s decision to detonate was based in part on concerns about drones carrying lethal devices into populated locations.
“Thankfully it turned out not to be real,” Kelly said, according to the Mercury News. “We are now more aware that this kind of equipment is flying around the atmosphere and they are more aware they need to better label it as a piece of scientific equipment.”
Read More: Defusing Roadside Bombs with Robots
While this marks the first time an ozonesonde has been blown up, bomb squads have been called in to investigate weird scientific payloads in the past. In May, a student’s science fair project, a replica of an oceanic vent, was detonated by a bomb squad in Prosser, Washington, while in 2012, a large container found on the campus of Oregon State University was investigated using a bomb-detecting robot that discovered stolen oceanographic equipment inside.
Get six of our favorite Motherboard stories every day by signing up for our newsletter.