Seven mercury tilt switches, detonating equipment and 700 rounds of ammunition were part of a suspected dissident republican weapons haul found by police in Belfast.
Firework powder and an assault rifle magazine were also recovered during the search of a house in west Belfast.
The raid on the property in the Broom Close area of Twinbrook was carried out on Sunday but police have only now revealed what was found.
Officer said other items were also seized during a subsequent search of a house in the Glenwood Walk area of Poleglass in west Belfast but declined to disclose what they were.
A 57-year-old woman and a 44-year-old man arrested on Sunday as part of the investigation remained in custody on Tuesday.
Police Service of Northern Ireland (PSNI) Detective Inspector Philip Montgomery, from the Serious Crime Branch, said: “We believe this is a significant seizure of munitions and bomb making components which was uncovered during a search of a house at Broom Close in the Twinbrook area.
“The items were concealed in a burn bag in the roof space. Inside the brown paper bag were more than 700 rounds of assorted ammunition packed into items of clothing, plastic bags and containers.
“Officers later searched another property at Glenwood Walk in Poleglass and several items have been taken away for detailed examination. We are not in a position at present to disclose what we have found there.
“We believe this is a significant find because it has taken off the streets materials designed to kill and injure.
“We apologise to local communities who were inconvenienced by Sunday’s searches. We would like to thank local political and community representatives for working with us during the search operation.
“I am sure the overwhelming majority of people in these communities are thankful that such items have been prevented from causing harm.
“We will continue to work with communities to reduce the threat posed by those involved in such activity and would ask people to contact police if they have any suspicions about terrorist activity.”