A Police officer investigating the theft of intelligence documents from the high-security Belfast police base in Castlereagh last month has travelled to the US to question a former employee at the station.
As part of the same investigation a number of searches were carried out in Belfast today.
A PSNI spokesman said: "As a result of planned searches of the New Lodge and Derry areas, police have seized a number of items. These searches are part of ongoing investigations, including inquiries into the Castlereagh break-in," he said.
During the theft a Special Branch officer was assaulted and documents taken when three men entered an office inside the Castlereagh complex on St Patrick's Day.
The theft prompted fears that the lives of police informers could have been put in jeopardy.
A 29 year-old man, Mr John O'Hagan, arrested after the break-in, was charged late last night with having documents likely to be useful to terrorists. It is understood these documents are unrelated to the Castlereagh break-in.
He was one of six people detained in Belfast and Derry last Saturday. The others, three men and two women, were released without charge earlier this week.
Sinn Fein has denounced the detentions as "ridiculous" and "highly provocative".
The party's Mr Alex Maskey said suggestions that Republicans were involved in the raid was "insulting to people's intelligence".
There was earlier speculation that the break-in had been an inside job. Commentators pointed to the way security controls had been evaded and the ease with which highly protected offices were opened. PA