A policeman has described the moment he found the driver of the truck involved in a huge chemical explosion in Queensland.

A truck driver who survived an enormous blast that destroyed a bridge and part of a Queensland highway complained of a bad headache when help arrived.

Police can’t believe the driver is alive after his B-double truck, carrying more than 50 tonnes of ammonium nitrate, exploded on the Mitchell Highway south of Charleville on Friday night.

The blast was so powerful it destroyed a bridge, hurling one 250kg chunk of reinforced concrete into the air. It landed 350 metres away.

A massive, vertical column of flame shot hundreds of metres into the air.

And police who were more than a kilometre away from the blast site were hit with sonic waves that felt like a kick to the chest.

Constable Kenric Head was one of those who’d felt the body blows from so far away.

When he reached the scene he said it didn’t seem possible that the man, lying under a tattered blanket on the roadway, could be anything but dead. But then he moved.

“He blinked,” Constable Head has told The Courier-Mail.

“We tried to talk to him about the footy but he didn’t follow the footy. But he did sort of joke with us, saying ‘I have got a f***ing headache’.”

The 29-year-old constable has described how Friday night’s emergency played out.

It began with reports from another Charleville police officer about a truck carrying highly flammable ammonium nitrate driving off a bridge into a creek about 30km outside the town. Then it blew.

Constable Head has told The Courier-Mail of driving towards the scene, as the other officer dodged massive chunks of concrete hurled into the air by the blast.

Despite the risks to their own safety, and concern that not all of the ammonium nitrate had been consumed in the initial blast, the police began searching the scene and found the truck driver.

He is in a Brisbane hospital being treated for extensive burns.

Investigations are continuing into the blast, which has sparked debate about how the transportation of dangerous cargoes are regulated.