PARIS - The brother of the French Jewish school killer who died in a hail of police bullets will be kept behind bars while he is investigated for possible complicity in the crime, the public prosecutor's office in France said on Sunday.Abdelkader Merah, 29, arrested last Wednesday as police laid siege to his brother Mohamed's Toulouse apartment following the killing of four soldiers, three Jewish children and a rabbi, was placed under formal investigation after four days of preliminary interrogation. "Police inquiries have produced grave and matching pointers that suggest his participation as accomplice in crimes relating to a terrorist enterprise is plausible," the Paris public prosecutor's office said in a statement.The inquiry will seek to establish whether Abdelkader Merah, who state prosecutors say is already known to security services for helping to smuggle Jihadist terrorists into Iraq in 2007, should stand trial. His wife was released.Abdelkader Merah was whisked to Paris on Saturday for further questioning and a police source disclosed he had said he was "proud" of his late sibling's killing spree.French President Nicolas Sarkozy summoned ministers and police chiefs to a meeting on Saturday to discuss the consequences of Mohamed Merah's massacre, which has raised troubling national security questions four weeks ahead of a presidential election.Sarkozy is facing an uphill re-election battle and his chief intelligence adviser sought to head off media questions about the handling of the affair in the southwest city of Toulouse.Abdelkader Merah, elder brother of the 23-year-old gunman who died in a hail of police gunfire on Thursday, was taken by car from police barracks in Toulouse for transfer to the capital, along with his wife, a judicial source said.Both were arrested on Tuesday as negotiators sought their help in trying to persuade Merah to turn himself in. Merah's mother, who was also arrested that day, was likely to be released later on Saturday, according to the same source.Merah was killed by a sniper after a gunbattle with police that ended a more than 30-hour siege at his Toulouse apartment, during which he admitted killing three Jewish schoolchildren, a rabbi and three soldiers in three separate attacks.Abdelkader Merah and his wife, whose name was not given, were transferred to a detention center at the headquarters of the DCRI domestic intelligence agency in Paris and will be brought before a judge to decide whether there were grounds for opening legal proceedings over possible links with Mohamed Merah's attacks, another source said on Friday.Police have found explosives in a car Abdelkader owned, according to the public prosecutor leading the case. He was already known to security services for having helped smuggle jihadist militants into Iraq in 2007.A police source said on Saturday that at a closed hearing in Toulouse he had declared himself "proud" of his brother's killings and had admitted helping Mohamed steal the scooter used in all seven murders. He had denied any knowledge of his brother's murderous plans, however, the source added.DCRI head Bernard Squarcini told the daily Le Monde on Friday that there was no evidence Merah belonged to any radical Islamist network and that he appeared to have turned fanatic alone.Yet investigators are still trying to establish whether the young Frenchman of Algerian extraction had any logistical or ideological support or was a genuine "lone wolf".Merah's brother, and a sister, were known to have studied the Koran in Egypt in 2010 and French police had in the past found links between them and a radical Islamist group based in southern France led by a Syrian-born Frenchman dubbed "The White Emir" by French media because of his fair hair and beard.The shootings shifted the focus of political debate away from France's economic woes and played to the strengths of Sarkozy as he fights for re-election in a two-round vote in April and May.Sarkozy's intelligence adviser, Ange Mancini, sought to head off increasing media debate about whether Merah could have been stopped before he started killing, saying the intelligence and police services had done an "exemplary" job and that it was always easy to ask after the fact if there were flaws.