Footage appears to show a dog being pulled along on a lead from a moving van.
The incident was captured on video by another road user appearing to show a person driving with one hand on the steering wheel and one hand holding the dog's lead.
The incident occurred at about 3pm on Saturday, October 16, on Tafarnaubach industrial estate in Tredegar.
Read more: The Welsh rescue centre at crisis point as owners keep handing in their dogs as 'fake' strays
The eyewitness who caught the incident on video, who did not want to be named, said: "I was so shocked. I came around the corner and I just saw a dog in the middle of the road.
"This man was hanging out of the van window with his arm and his body running the dog. He was going quite fast.
"It was nearly going under the wheels. He was going up and down the industrial estate with the dog like that. I wanted to get out and take the dog."
The woman said she reported the incident to Gwent Police and the RSPCA.
A spokesperson for the RSPCA said: "We’re aware of this incident and encourage anyone concerned about an animal’s safety to please contact the RSPCA’s emergency helpline on 0300 1234 999.
"Unfortunately we are unable to discuss complaints about specific individuals. We understand how frustrating that is for animal lovers but releasing information could prejudice a future investigation or could lead to us being fined.
"We are so grateful to people who report suspected animal suffering to us and we would like to reassure people we will always look into and, if necessary, investigate any complaints made to us about animal welfare."
A Gwent Police spokesperson said it had received a report of the incident "shortly before 4.50pm on Saturday, 16 October".
"It happened in the Tafarnaubach Industrial Estate, Tredegar," the spokesperson added.
To get the latest email updates from WalesOnline click here.
