It is one line of inquiry police say they are investigating following a security alert in Lisburn on Saturday.
A controlled explosion was carried out on the object after it was found in Market Place.
It was made safe and removed for examination during a security alert which lasted several hours.
The murder bid is being investigated by detectives from the PSNI’s Terrorist Investigation Unit.
Police say a vehicle was seized during a follow-up operation in the Lagmore area of west Belfast on Saturday night.
Supt Brian Kee said: “Our investigation into the circumstances surrounding this security alert is at a very early stage.
“We are following a number of lines of enquiry, one of these is that the device may have fallen from a vehicle.
“As part of a follow up operation in the Lagmore area of Belfast last night, a vehicle was seized for examination.
“We are keen to hear from witnesses or anyone who was in the Market Place area of Lisburn yesterday and who may have information that could assist the investigation.”