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, spokesperson for the emergency services in the region, told AFP.

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

The injured were in serious condition, Ntladi said. Six firefighters also suffered minor injuries.

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

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

Witness Jean Marie Booysen described a "huge jolt" shortly after 6:30 a.m. local time.

"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 said she later learned young neighbors had died from "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, described a series of explosions and said people nearby had felt the blast.

"I think I was 50 meters away from the scene and when the third one exploded, I was about 400 meters away," he said. "We did burn behind our backs."