Rebekah Brooks, a former editor and close confidante of Rupert Murdoch, was arrested for a second time on Tuesday in a phone-hacking scandal that has rocked the British establishment and embarrassed Prime Minister David Cameron.
A source familiar with the situation said Brooks and her husband Charlie, a close friend of Cameron, were detained by police at dawn and had been taken for questioning at separate police stations.
They were held on suspicion of conspiring to pervert the course of justice in the long-running saga and were among six people arrested in coordinated raids across Britain.
Brooks, her husband and three others were later released on police bail until a date in April. The sixth person was bailed on Tuesday night with the same conditions.
The 43-year-old former News of the World editor, instantly recognisable for her long red hair, was arrested in July over different allegations but only after she arrived at a London police station by appointment.
News Corp, Murdoch's media empire, owned the now-defunct News of the World Sunday tabloid at the centre of the investigations. It declined to comment on the arrests although it did confirm that Mark Hanna, the head of security at its British newspaper arm, had also been held.
The police did not name those it had arrested.
Conspiring to pervert the course of justice, which in this investigation has meant the destruction of email evidence, could result in a more lengthy jail sentence than that handed down for hacking into mobile phones to search for gossip and story ideas.
The News of the World's former royal reporter Clive Goodman and private detective Glenn Mulcaire were jailed for four and six months respectively in 2007 for phone-hacking offences.
A judge handling the civil law suits brought against News Corp has already criticised the company for deleting emails.
The stream of allegations and arrests have shaken News Corp and damaged police and politicians from all major political parties, revealing the extremely close ties between the media and elements of the political and police establishment.
The 168-year-old News of the World was shut down in July at the height of the scandal, while two of Britain's most senior police officers quit their posts after being accused of failing to properly investigate the allegations.
The latest arrests will be uncomfortable for Cameron, who admitted this month that he had ridden a horse given to the Brooks couple by the police, in an episode dubbed Horsegate.
Cameron, who has sought to downplay his wealthy background which is regarded as an electoral weakness, said he had been friends with Charlie Brooks, a racehorse trainer, for more than 30 years.
Asked on Tuesday how concerned the prime minister was about Charlie's arrest, a spokeswoman for Cameron said: It's an operational matter for the police. She declined more comment.
Cameron's judgment was called into question after his decision to appoint another former News of the World editor, Andy Coulson, as his head of communications.
Coulson has denied all knowledge of phone hacking, but he resigned from his post at No 10 Downing Street in January last year and was later arrested by police investigating hacking.
Charlie Brooks was dragged into the scandal last July when police seized a bag containing a laptop computer and personal documents from close to the couple's London apartment.
Brooks, who attempted to reclaim the bag, said at the time that the items had nothing to do with his wife and had simply been misplaced following a mix-up with a friend.
He had been due on Tuesday to attend the Cheltenham Festival, one of Britain's most prestigious horse racing events. In a column for the Telegraph newspaper he described the opening day of Cheltenham as his happiest moment of the year.
Instead, the six were held following a consultation with the Crown Prosecution Service, the department which prosecutes criminal cases investigated by the police.
(Reporting by Kate Holton, Georgina Prodhan, Adrian Croft and Michael Holden; editing by Robert Woodward)