A truck driver is fighting for his life after his vehicle carrying more than 50 tonnes of ammonium nitrate rolled and exploded in outback Queensland.

A truck driver burned in a massive explosion in outback Queensland is fighting for his life. The area the accident occurred in remains too dangerous to enter.

The 33-year-old Mackay man is in a critical condition after he and seven others were caught up in Friday night’s huge blast on the Mitchell Highway about 30km south of Charleville.

The man’s truck was carrying more than 50 tonnes of ammonium nitrate when it exploded after rolling about 10pm (AEST).

He’d been transporting the chemical substance from Gladstone to South Australia but is now in the Royal Brisbane Hospital with life-threatening burns and head injuries.

The blast destroyed a bridge and injured a police officer and four firefighters who had been called to the crash scene, as well as two motorists who stopped to help.

Two fire trucks were severely damaged, and shock waves rattled houses in Charleville, making residents think there had been an earthquake.

A two-kilometre zone around the blast site has been cordoned off and a scientific team is waiting in Charleville until the area is safe to enter.

Assistant fire commissioner for the southwest Tom Dawson said some ammonium nitrate was still burning following the explosion, which had damaged foliage up to three kilometres away.

Two firefighters remain in hospital in Toowoomba in a stable condition, while two others were released from Charleville Hospital on Saturday with minor burns and cuts and bruises.

A police officer who suffered cuts was also released from hospital on Saturday.

Queensland Transport Minister Scott Emerson said a 4WD track would let cars detour the blast site but bigger trucks couldn’t go around the blocked highway, which links Charleville with Wyandra and Cunnamulla to the south.

Ammonium nitrate is used in the mining sector as an explosive ingredient and as a fertiliser in agriculture.