Police and fire brigade investigators are probing the cause of the blaze which tore through the Longscar building in Seaton Carew last night.
Cleveland Fire Brigade was called to the scene just after 8pm and sent eight appliances and two aerial ladder platforms to the scene.
Hundreds of people turned out last night to watch, with police putting up a cordon and closing the road to traffic.
Flames were seen burning through the roof, with smoke billowing 60ft in the air and out to sea as scores of firefighters tackled the blaze.
Firefighters remained at the scene until around 8am.
The full scale of the damage to the landmark building is clearly visible today.
A Cleveland Police spokeswoman said: "Police received a report of a fire at the Longscar Centre on The Front in Seaton Carew at 8:20pm last night, Tuesday 8th May.
"Enquiries are still at a very early stage and officers are working with Cleveland Fire Brigade to establish the cause of the fire."
Flames have been seen from the roof, with a large amount of smoke caused by the fire.
Freelance journalist John David McDade, 37, from Glasgow, is in Hartlepool visiting family and said: "I just saw a plume of white smoke in the air and then saw one fire engine and then the platform.
"Smoke is coming out of the roof.
"We've counted and there must be about 60 firefighters.
"The police then kept the crowd back and over the space of 20 minutes, half an hour, the building is now just a shell.
"There's a good couple of hundreds people here and there are two cordons, one at each end."
The Longscar centre, which is privately owned, has been vacant since 2009.
An attempt by Hartlepool Borough Council to force the owners to sell failed following a public hearing.
Last November, the council agreed to a programme of work to upgrade the existing car park near the centre, changes to the layout, landscape improvements and the provision of seating.
The council had to redraw their plans after a Compulsory Purchase Order for the derelict Longscar Centre was rejected.