Police have warned dozens of republicans that their lives are under threat from loyalist paramilitaries.
A document was believed stolen from Castlereagh security complex
It is linked to the discovery of a document believed to have been taken from an Army office in the Castlereagh security complex last year.
More than 20 soldiers were transferred to other duties while the investigation into the missing document began.
The republicans, from the Short Strand, were told their details had been found in the possession of paramilitaries.
Sinn Fein's Alex Maskey said more than 50 homes were visited by police.
"This development is clearly of concern to the people involved directly, their families and the wider community in the Short Strand," he said.
Sinn Fein's Alex Maskey said it was a cause for concern
"It has been well over a decade since such a large number of republicans were visited in an operation like this in the city."
Police said they recovered a document thought "linked to a breach of internal security in Army offices in July 2004".
The PSNI said in a statement that "as a result, police are now warning a number of people about their personal security".
Police would not say from where exactly the document was recovered.
Security force sources have indicated that the document was of a type used by the military to assist them in monitoring terrorism suspects.