We're appealing for witnesses following a report of criminal damage on the M4, near junction 24.
Officers are investigating a report of criminal damage, following an altercation between two drivers on the M4, heading West near junction 24, at around 5.40pm on Tuesday 19 September.
The incident involved two cars - a dark grey Skoda Octavia with a company logo on the front and a silver BMW X3.
The front passenger from the BMW allegedly exited the vehicle and reportedly used a knife to cause damage to the bonnet and front passenger window of the Skoda Octavia before returning to the BMW and leaving the scene.
A 22-year-old man from the Caerphilly area was arrested on suspicion of drug driving, criminal damage and possession of an offensive weapon.
A second man, also aged 22 from the Caerphilly area, was arrested on suspicion of possession of an offensive weapon and criminal damage.
Both men have since been released on bail as our enquiries continue.
We are appealing for dashcam footage or information from anyone who was driving along this stretch of road between 5.15pm and 5.30pm on Tuesday 19 September.
Anyone with information is asked to call us on 101, quoting log reference 2300318335 or send us a direct message on social media.
Alternatively, you can contact Crimestoppers anonymously on 0800 555111 with details.