Published Tuesday, 12 March 2013
The security alert closed the M5 for almost 24 hours at the weekend. (© Presseye)
The weapon was found on the pathway between Hazelbank and Duncrue on Saturday morning, near to where the explosion occurred.
Police are also investigating the possibility that a call made from a public phone box outside shops at the junction of Antrim Road and Fortwilliam Road in north Belfast, at around 7:40pm on Saturday is also linked to the incident.
"As part of our follow-up inquiries, we now believe that the discovery of a suspected firearm on the towpath could be linked to the attack," Senior Investigating Officer, Detective Chief Inspector Karen Baxter explained.
"I am very keen to speak to anyone who may have been in the area of the towpath before midday on Saturday."
DCI Baxter also urged anyone who was at the shops in the area where the phone call was made to come forward.
"There is a takeaway restaurant, an off-licence, and a bank in this area so it would have been busy at this time," she said.
"I would appeal to anyone who was in these areas at the times specified, to contact us immediately on 028 90 700303."
Three officers narrowly escaped injury after a device exploded within metres of them on the Duncrue towpath at around 9.15pm on Saturday.
Police were lured to the area after two phone calls earlier that day during a security alert that closed the M5 between Hazelbank and Greencastle for almost 24 hours.
DCI Baxter said it was a "sophisticated and planned" attempt to murder police officers.