Police are appealing for information after a metal balloon caused a massive blackout around Dresden in Germany.
Authorities said the "commercial foil balloon" caused a short-circuit at an electricity substation in the eastern German city on Monday afternoon.
The subsequent power outage affected local hospitals, trams, factories, and an estimated 300,000 households.
Dozens of people were reportedly trapped in elevators for one hour until electricity was restored.
Claudius Rokosch, a spokesperson for the utility company SachsenEnergie, said on Tuesday that a charred, aluminium-covered balloon had been found at the substation in the district of Zschachwitz.
The balloon featured a clear warning not to fly it near electrical wires, Rokosch added in a press release.
Dresden police have confirmed in a statement that they were investigating whether any criminal offence had been committed.
"According to current information, a commercial foil balloon triggered the power failure," the statement read.
"Apparently, the balloon had come between two live conductors and triggered a short circuit, which then led to the power failure."
Police spokesman Thomas Geithner said investigators do not currently have any evidence that the balloon was intentionally flown into the overhead cables.
Geithner added that nobody had claimed responsibility for the incident, likely ruling out any politically motivated attack
"We are currently working on the assumption that at best it was careless, or simply a coincidence,” he said. "But we can’t 100% rule out foul play either."