Two children have been flown by air ambulance to Southmead Hospital in Bristol.
An adult has been taken by ambulance to Morriston Hospital. Their injuries are described as serious.
The road will remain closed overnight and diversions are being put in place.
Around 14 properties have been evacuated and Neath Port Talbot Council have opened a rest centre with full support for these residents.
The cause of the explosion is under investigation.
Kirsten Williams was in her in-laws garden when the tragedy happened she told us: "We were all sitting outside. Just down the road from the explosion. The conservatory shook. A massive bang. My mother-in-law suggested it was a car crash or a lorry. I said 'no..that's an explosion.' My father-in-law rushed up the drive and saw people running across the road and called us up. I grabbed my 17 month old son and off we went to see what had happened. What shook me the most was a small baby teddy bear was there laying on top of the car roof."
The emergency services are at the scene.
A number of properties and vehicles in the street have been damaged and the area has been evacuated.— South Wales Police (@swpolice) June 24, 2020
One adult and two children, have been injured in the incident.
We remain at scene with emergency service colleagues and ask people to continue to avoid the area.
People are being urged to avoid the area.