An overflow of dielectric oil occurred at night on the 225,000-volt transformer supplying the melting furnace of a steel mill subsequent to a malicious act; the transformer switched into security mode. After scaling the double-fenced enclosure, one or two individuals penetrated into the protected distribution station and opened the oil drain valve. The transformer was damaged; 30 tonnes of liquid and solid waste were discharged. The steel mill and rolling mill were shut down during the repairs, and the stockpile of billets was insufficient to keep the rolling mill operating. Property damage was estimated at €87,000, while operating losses amounted to €2.5 million. The operator installed a retention device as well as a monitoring camera.