Eighty people and a residential complex were evacuated after flooding in Skewen.
Dozens spend the night in temporary accommodation after "at least eight streets" suddenly flooded on Thursday afternoon.
Authorities say that it is too early to tell how it happened but it is understood that they are looking that it might have been caused by a "burst mineshaft".
Skewen has had problems in the past with disused mine workings. There area is has many historic shallow coal mine workings under ground. There were a number of collieries around the village and nearby drift mines. There have previously been problems on Ormes Road when the surface dropped half a metre which were blamed on abandoned mine workings.
The area flooded on Thurday at Goshen Park is not far from Ormes Road and the colour of the water and slurry that flooded through the area has led to speculation it had built up under pressure in disused mine workings littered with rusting iron materials before bursting out.
Jeremy Miles MS said that early indications were that it "may involve disused mine workings".
Here is what we know so far.
Residents rescued on pick-up trucks
Nobody has been injured in the incident, which saw people rescued on pick-up trucks and pets carried to safety.
A video, which was posted on social media on Thursday afternoon, showed water flowing down the street with a concerned resident asking for help.
A woman can be heard in the footage saying that the whole street in Goshen Park is flooded and "there's water coming out of the houses".
Resident John Thomas came home from a funeral on Thursday afternoon to find that his home had been flooded.
"I came home to a lake, basically, the water was around the level of the bottom of the door so we couldn't go in," he told BBC Radio Wales. "We had to stand there and watch this yellow coloured water piling up and up and up. It was like lake.
"We are on a dip and you could actually see it gradually coming up to the next drain, then the next drain and then when they were getting full there was bubbling coming up. It wasn't very pleasant."
He is now staying with his daughter in Bryncoch but he didn't have a chance to move anything in the house because they were out at the time.
"I tried to get in but the water was up to nearly my waist," he said. "The back garden, I have always wanted a swimming pool, but not that colour."
Major incident declared
On Thursday night it was confirmed that a major incident had been declared after "at least eight streets, including Goshen Park, flooded and a large number of properties needed to be evacuated".
A multi-agency statement, issued by South Wales Police, added: "Everyone who was evacuated has been found accommodation for tonight, estimated at around 80 residents.
"There have been no reported injuries and we ask people to continue to avoid the area. The cause of the flooding is being investigated and the water level will continue to be monitored."
What caused the flooding
Large parts of Wales were affected by flooding after Storm Christoph brought heavy rain, but the worst of the storm had passed by the time of the flooding on Thursday afternoon.
Authorities are still investigating the cause, but the early indications are that it is linked to a disused mine in the area.
Local MS Jeremy Miles said: "I have been in touch with Neath Port Talbot Council and Welsh Water in relation to the serious flooding in the Skewen area, which is affecting homes in my constituency.
"Both organisations, together with NRW, Coal Authority and other agencies and services are at the scene, supporting residents including those who have unfortunately had to leave their homes.
"Current indications are that it may involve disused mine workings but the volume of water is too great to be certain."
He said that all the frontline agencies and services are involved.
Local resident John Thomas said he had been told they weren't going to be able to go back for a day or two.
He said he was convinced it had been caused by the mine, telling BBC Radio Wales: "You can tell my the colour of the water, it is like an orange colour."
High levels of iron in water caused by rusting mine equipment abandoned underground is one potential cause of the orange colour.
The help in place for local residents
Neath Port Talbot council chief executive Karen Jones said: “Council officers have been on site since around midday and there will be a continued council presence in the area throughout the night.
“Our main focus at present is on continuing to support residents who had to leave their homes and ensuring others have a safe place to go if further evacuations are necessary. A local rest centre is on standby where measures have been put in place to protect against the spread of Covid-19.”
People are being asked to stay away from the area this morning as heavy lifting gear is being brought in to help with the clear up.
Anyone who needs help is asked to contact Neath Port Talbot Council's emergency number on 01639 686868 .