Murder squad detectives are trying to find dash cam footage of the scene where a former Real IRA boss was shot dead last week.
Aidan O'Driscoll, 37, was shot a number of times in an ambush in the Blackpool area of Cork city at about 5pm last Wednesday.
It is understood he may have been the victim of a feud within dissident republicanism.
Detectives hunting the killers said the getaway car used in the murder, a Nissan Almera with the registration number 01-TS-1312, was in the Blackpool area for a number of hours before O'Driscoll was targeted.
"We are aware that a number of people who were in the area at the vital time have not made contact with the Gardaí," a spokesman said.
Gardaí urged taxi drivers and other motorists or cyclists who have a dash cam and were in the Blackpool area from 2pm last Wednesday to come forward.
Officers also appealed for witnesses who might have seen a white Vauxhall Astra van with the registration number 99-G-12357, a red Opel Astra car or a black Toyota Avensis on the day of the murder, particularly in the Blackpool area from 2pm to 5pm or in the Killeens area from 2pm to 6pm.
O'Driscoll, from Ballyvolane in north Cork, was shot dead on Old Commons Road in the city.
Nicknamed the 'Beast', he was a one-time ally of Real IRA chief Alan Ryan, who was shot dead in Dublin in 2012.
It is understood he had not been active in the terror group for some time, having been apparently expelled.
He was shot in the leg in a so-called punishment attack carried out by former republican allies in 2013.