Detective Donohoe was shot dead during a robbery at a credit union in Bellurgan, near Dundalk in January.
Gardaí are seeking information on a white articulated lorry that was parked on Shean Road, close to the border village of Forkhill at 9.45pm on the night Detective Donohoe was murdered.
In a statement yesterday (Tuesday) evening, Gardaí said a number of people were seen around the lorry, which may have been broken down.
“We want to establish the identity of the driver/owner of the vehicle and the identity of any person present with this lorry on the January 25,” a gardai spokesperson explained.
“We also want to establish the identity of any person who may have been involved in the recovery of the vehicle, the identity of any person who may have been involved in the service of the vehicle on the 25 January and identify the drivers of any other vehicles that may have been travelling on the Shean Rd, Forkhill at 9.45pm.”
This appeal comes after police in the North seized mobile phones and documentation in searches carried out in four houses, in South Armagh on Monday night.
No arrests were made in the operation which police confirmed was in support of the Garda investigation. Anyone with information is being asked to contact Gardai at Dundalk on 042 9388400.