Police have released photographs of two vehicles they believe may have been used in an attack on prison officer Adrian Ismay.
The father of three died after being injured by a dissident republican bomb which detonated under the van he was driving to work on March 4 in east Belfast.
Police are appealing for information on a red Citroen C3 with the number plate SKZ6662, which is believed to have been used by those planting the device.
They also want information on a silver Skoda Fabia KFZ2352, which is thought to have been used before and after the incident by those involved.
Detective Chief Inspector Richard Campbell said: "In particular I am appealing for any sightings of this vehicle, on the move or parked up, between 7pm on the evening of Thursday 3 March and 4am during the early hours of Friday 4 March.
"It is my understanding that a male was dropped off in this vehicle in Pilot Street in the Docks area of Belfast at around 3am on Friday morning and I am appealing for anyone who saw this, or who knows the identity of this male to come forward to police."