Dissident republican weapons were found stored in a boiler house in west Belfast after it caught fire.
The haul, which police believe belonged to the New IRA, included shotguns, assault rifles, pipe bombs and ammunition.
It's thought some of the weapons had been used in prior attacks on officers.
The discovery was made when the Fire Service was called to the scene of a blaze in the rear garden of a property in Rodney Drive earlier this week.
As the fire developed, a number of the rounds exploded, causing “significant danger” to local residents and firefighters.
Police condemned those who stored them there as “incredibly reckless”.
A spokesperson added: “It beggars belief that anyone would store items as volatile as bombs and bullets in a hot environment.
“Anyone with an ounce of sense would know that live ammunition and pipe bombs mixed with heat is a recipe for carnage.”
The weapons, which were stored on top of the hot boiler, included:
- Two AK-47 assault rifles
- Two sawn-off shotguns
- A high-power rifle with silencer
- Three pipe bombs
- Over 100 rounds of live ammunition.
Police said they "firmly believe" they belong to the New IRA.
They said one line of enquiry is that the AK-47s were used in attempts to murder police officers in Rosnareen in November 2015, and on the Crumlin Road in January 2017.
"The Crumlin Road shooting in particular, also demonstrated recklessness and showed total disregard for members of the public as gunmen fired bullets into the filling station forecourt and shop, narrowly missing customers and passing motorists," a spokesperson added.
Detectives are now investigating the circumstances surrounding the discovery.
It's believed the weapons may have been moved there on Monday evening some time after 9.30pm and anyone who was in the area, or saw anything suspicious in the alleway behind Rodney Drive, is asked to come forward.
Police went on: “It is clear that whoever placed these weapons in this boiler house was incredibly reckless.
"What is more concerning is that they actually didn’t care at all that they were putting the lives of this entire family neighbourhood at significant risk of death or injury.
“These people are beneath contempt and I am asking for the community to stand up against these parasites.
"They don’t have your best interests at heart, instead they want to control and exploit the decent people trying to live their lives and raise their children.
"They clearly don’t care if they harm you in their sinister activities. This is not want anyone wants for the future.
“Anyone who heard or saw anyone acting suspiciously in the laneway at the back of Rodney Drive should contact police on 101."
A 35-year-old man who was arrested under the Terrorism Act on Wednesday has been released unconditionally.