Arsonists have caused an estimated £1m worth of damage at a scrap-metal recycling plant in the Black Country.
Emergency services were called to a fire in European Metal Recycling Plant in Downing Street, Smethwick, at about 2240 GMT on Tuesday.
Police said the offenders probably walked to the site from Booth Street Metro and left by the same route.
The firm's Wednesbury plant was also set alight on 27 October and the two arson attacks have been linked.
Anyone with information or who saw people acting suspiciously in the area is asked to call West Midlands Police.
Det Sgt Chris Vyse said: "We are doing everything we can to catch those responsible for the fire.
"They have caused a substantial amount of damage and someone could have been seriously hurt."