Police in the North have said it is too early to link an explosives haul to any particular terror group.
An estimated 1.5kgs of explosives, believed to be Semtex, were found at the Maeve House tower block in the mainly nationalist New Lodge area of north Belfast on Monday.
It is thought there was enough to make three under car booby-trap bombs.
Chief Superintendent Chris Noble from the Police Service of Northern Ireland (PSNI) said: "These items will now be subject to a detailed forensic examination. Until this has been completed, it is too early to link these items to any particular group. Our investigations are currently ongoing and we are following a number of lines of enquiry.
"This was a significant recovery and we want to make sure that we gather every single piece of available information to assist us with our inquiries."
The discovery followed a tip-off from a member of the public, the PSNI said.
Mr Noble added: "This seizure demonstrates that when people provide us with information, we will act on it to ensure everyone in our community is kept safe."
The North’s Secretary Theresa Villiers said it highlighted the severe threat and need for ongoing public vigilance.
Deputy First Minister Martin McGuinness also said he was pleased the weapons had been taken off the streets.
Last month, an armour-piercing improvised rocket, two anti-personnel mines, several pipe bombs, magazines and ammunition for an assault rifle, bomb component parts and command wires were recovered from a terrorist hide in woodland near Larne, Co Antrim.
And, in March, police found bomb-making parts and explosives at the Carnfunnock Country Park, also near Larne.