JOHANNESBURG, South Africa -- Ten people died and around 40 others were injured when a fuel tanker exploded in Boksburg, a South African city east of Johannesburg, emergency services said Saturday.

The tanker, transporting liquefied petroleum gas (LPG), was caught beneath a bridge close to a hospital and houses on Saturday morning.

"We received a call at 0750 telling us a gas tanker was stuck under a bridge. Firefighters were called to extinguish the flames. Unfortunately, the tanker exploded," William Ntladi, spokesman for the emergency services in the region, told AFP.

One of those injured was the driver who has been taken to hospital, he added.

He said the death toll had risen to 10 from the nine reported earlier.

Of those injured, around half were in a serious condition while 15 others were seriously hurt but in a stable condition.

Six firefighters also suffered minor injuries, Ntladi said.

Videos on social media showed a huge fireball under the bridge, which the tanker appeared to have been too high to go under.

It was carrying 60,000 litres of LPG gas, which is used especially in cooking and gas stoves, and had come from the southeast of the country.

Witness Jean Marie Booysen described a "huge jolt" in the early hours of the morning, shortly after 6:30 am.

"Today is indeed a very sad day in our little suburb," she said, standing near a forensics team combing the scene.

"I went upstairs to have my cup of tea and I saw immense flames, I thought a house was on fire."

She said she later learned of the deaths of "two children here across the road, 16, the girl, and 25, the boy, who came and did my lawn every weekend for me".

Another witness named William, who did not give his surname, said people nearby had felt the blast.

"I think I was 50 meters (164 feet) away from the scene and when the third one exploded, I was about 400 meters away."

"We did burn behind our backs", he said.