Police in Caerphilly are appealing for information to track down two cars which may have been used in an attack that has left a 32-year-old man critically ill in hospital.
The victim was found on a pathway near to Addison Way, Graig-Y-Rhacca, early on Friday last week.
Gwent Police said they want help to find a black Mitsubishi L200 Warrior, registration VX03 KHD and a Daihatsu Fourtrak, registration K727LSB.
Two local men, aged 20 and 21, have been arrested and released on police bail.
The man was found with serious head injuries shortly before 1.40am on Friday.
He was taken to the Royal Gwent Hospital in Newport but later transferred to the University of Wales Hospital.
The man is said to be in a critical but stable condition.
Gwent Police said the assault was thought to have happened some time between 6pm Thursday and 1am Friday.
Anyone with information should contact Gwent Police on 101 or Crimestoppers on 0800 555 111.