Police have released photos of a man they want to trace after a bottle of hydrochloric acid was left on a train, causing a station to be shut and a major response from the emergency services.
British Transport Police were called to Middlesbrough station at 7.16pm yesterday after someone reported a burning smell on board a Northern Rail train to Darlington.
Firefighters were called and the train and station were evacuated as a precaution due to the fumes.
Experts from the fire service later identified the liquid left in a drinks bottle in the middle of the train as a form of hydrochloric acid, which is highly corrosive.
Detective Inspector Mick Jackson of British Transport Police said: "We have been undertaking inquiries, including checking CCTV, to ascertain how and why the bottle came to be on the train, and believe the man pictured may be able to assist them with their inquiries.
"If you know him, we would like to hear from you."
Police do not believe the incident was terror-related.
A number of emergency services vehicles, including at least one ambulance, were called to the station. No one was hurt in the incident.
Anyone with information should call 0800 405040 quoting the log reference B4/ NEA of 14/01/2012.