The fire was reported at approximately 2.45am on Monday, August 16. No one was injured.
The fire is being treated as deliberate and two people, a 17-year-old local boy and a 19-year-old girl have been arrested on suspicion of arson with intent to endanger life and released on police bail pending further enquiries.
If anyone has any information about the incident or if anyone saw anything suspicious at the time and place they should contact Gwent Police on 01633 838111 or call Crimestoppers on 0800 555111.