Police want to speak to two men who were spotted on waste ground near a police station targeted in a mortar bomb attack.
The men were seen on waste ground on west Belfast's Ballygomartin Road between 5.30pm and 6pm last Tuesday – three days before the device was discovered.
Residents were evacuated from up to 70 homes and two primary schools were shut in a security alert on Friday, which ended shortly before noon the following day.
The area was closed after an off-duty police officer and a passing taxi driver spotted the device at around 7.15am on Friday.
Police said the viable mortar, which they believe was driven to the area, failed to go off.
The investigation is now focusing on last Tuesday between 5.30pm and 6pm.
"Police wish to speak to anyone who may have been on waste ground area on Ballygomartin Road between 5.30pm and 6pm on Tuesday, March 12," a PSNI spokeswoman said.
"In particular, police want to speak to two men who were seen in this area at that time in order to eliminate them from this enquiry." The mortar was defused by Army experts.