Security breach suspect held

Castlereagh is the PSNI's Belfast headquarters

Police in Northern Ireland have been given more time to question a person held over a security breach at Belfast's police headquarters last month.

Detectives were granted an extension beyond the original 48-hour holding period which expired on Monday.

Five other people detained in a series of police operations in Belfast and Londonderry on Saturday have been released without charge.

A Special Branch officer was assaulted and documents taken when three men entered an office inside the Castlereagh complex, in the east of the city, on St Patrick's Day.

'Republican involvement'

The theft occurred in the source handling unit, which is used as a "link-point" for security force informers and their police handlers.

Security sources have linked the incident to the Provisional IRA.

The police investigation is now concentrating on the possibility of republican involvement, specifically the Provisional IRA, security sources have told the BBC.

None of those arrested, four men and two women, is connected to the security forces.

A civilian employed at Castlereagh had also been held for a time.

On Saturday, a Sinn Fein spokesman said republicans had played "no part in the raid on Castlereagh".

John Reid: Established review

He said it was an "inside job" and claimed the arrests were an "attempt by Special Branch to cover up the truth".

Days after the breach, it emerged that the office was only moved to that room from another part of the building a week previously because the complex was being refurbished.

Two separate investigations into the incident are taking place - the police's own and an inquiry by former senior civil servant Sir John Chilcot who will report directly to Northern Ireland Secretary John Reid.

Sir John Chilcot will be assisted by Colin Smith, a former Thames Valley chief constable and a former member of Her Majesty's Inspectorate of Constabulary.

The review will proceed in parallel with the criminal investigation which is being led by Detective Chief Superintendent Phil Wright, the most senior detective in Belfast.

Special Branch deals with intelligence work, some relating to informers, and has an anti-terrorism role in Northern Ireland.

One of the main police centres for the interrogation of terrorist suspects was located at Castlereagh. It closed at the end of 1999.