Two people have been injured after a huge blast at a former steelworks in Redcar.
A witness described seeing a massive fireball at the former British Steel Lackenby Works.
It has been declared a major incident by police.
The area has been cordoned off as police and fire officials investigate the cause of the blast.
Emergency services were called at around 2pm.
Both men injured are believed to be contractors working on demolition at the site.
Did you see what happened? Email webnews@mirror.co.uk
An employee told Teesside Live: "It was the biggest bloody fireball I’ve ever seen. It was massive.
"I can only describe it as something you would see in the Gulf War. It went higher than the big tower.
"The ground shook and I heard a muffled sound. A bit like an airplane flying over. But I thought hang on, that’s way too close.
"That’s when I saw the huge fire ball go up.
"I was expecting metal and things to start flying everywhere but it didn’t happen like that. It was as though all the gasses just went up at once."
A spokesperson for the North East Ambulance Service said, "We were called at 14:10 to reports of an explosion at British Steel Lackenby Works in Middlesbrough.
"Six resources have been dispatched to the scene including our Hazardous Area Response Teams.
"The number of casualties are yet to be confirmed. Fire are also in attendance."
A Cleveland Police statement said: “Cleveland Police officers and emergency services colleagues remain on scene at the former SSI site in South Bank, which was evacuated following a report of a fire at around 2.15pm today.
"The fire is ongoing, however, it is contained and officers and Fire Brigade colleagues will remain on the scene overnight to continually monitor the situation.
"The cordon put in place has been extended to 250 metres. There are no residential addresses in the cordoned area and there is no danger to members of the public.
"This has been declared a major incident and there is a multiagency collaborative response to this, with the situation being monitored continually."
