Detectives get more time to question Stakeknife
Detectives have been granted additional time to question a man widely named as the British Army's notorious IRA agent Stakeknife.
A team of independent detectives probing claims of murder, kidnap and torture detained a 72-year-old at an undisclosed location on Tuesday, a statement from Operation Kenova said.
Officers have subsequently been allowed a further 36 hours to question the man.
In 2003, Stakeknife was widely named as west Belfast man Freddie Scappaticci but he has always strongly denied the allegation.
Bedfordshire Police Chief Constable Jon Boutcher is investigating the high-ranking mole who reputedly led the republican organisation's "nutting squad", an internal security unit which brutally interrogated and murdered suspected spies during the Troubles in the North.
Dozens of detectives are probing more than 50 murders.
Almost 50 detectives have been working on the Stakeknife investigation.
As well as multiple murders, the investigation team is examining evidence of other alleged offences committed by Stakeknife during the Troubles, including attempted murders and unlawful imprisonments.
A number of Police Ombudsman for Northern Ireland investigators are understood to be present following the arrest.
The independent ombudsman investigates current and former police action in Northern Ireland.
The independent team of detectives began investigating after the former director of public prosecutions in Northern Ireland, Barra McGrory QC, referred multiple allegations to the PSNI.
The PSNI decided to call in external help from officers outside Northern Ireland.
The update on the investigation added: "Operation Kenova is a complex and wide-ranging investigation which was launched in June 2016 to investigate allegations of murder, kidnap and torture dating back to the 1970s.
"So far the team has engaged with more than 40 families and processed more than 500,000 pages of information generating 1,500 lines of inquiry.
"Anyone with any information relating to Operation Kenova can contact the team by calling 01234 858298 or by email email@example.com."