A woman has been arrested on suspicion of a racially-aggravated public order offence after an “inappropriate” comment was made, police said.
The 62-year-old is being held over a Facebook post advertising the recruitment of taxi drivers.
A taxi firm advertised for staff on social media, but said it did not want to employ Pakistani or “dark” drivers.
South Wales Police said it took “such matters seriously” and was working with Neath Port Talbot council.
The post was criticised by former Plaid Cymru leader Leanne Wood, who tweeted that it “disgusted” her.
Publishing an advert which discriminates on the basis of a protected characteristic, which includes race, is unlawful under the Equality Act 2010.