During a later inspection of the network’s electrical equipment, the company’s engineers discovered a dead slug, measuring about 2 to 3 centimeters (0.7 to 1.1 inches) long.

According to a company spokesman, the slug had burned to death after touching an electrical cable leading to the mass power failure.

Although it was discovered on May 30, shortly after the outage, the reason for the disruption wasn’t revealed for more than a month.