French police took Abdelkader Merah, elder brother of Toulouse killer Mohamed Merah, to intelligence headquarters in Paris for investigation on Saturday, Reuters reported.

The Toulouse killings, in which seven people including three children were killed by the self-proclaimed al Qaeda activist Mohamed Merah, have raised concerns about the national security and efficiency of the French intelligence.

Both Merah brothers were reportedly under French intelligence surveillance for years for their leanings towards extreme salafist views, but the police had not taken any measures to follow them up.

Abdelkader was arrested along with his girlfriend on Tuesday as negotiators sought their help to convince the killer Merah to give himself up to the police. Merah was shot dead by the police, after an exchange of gunfire in his apartment where he was holed up for more than 30 hours.  

Merah's mother was also detained on the same day but was released without charges on late Friday, reported quoting unofficial sources.

Abdelkader and his girlfriend, whose identity is not yet revealed, where whisked to a detention center at the DCRI domestic intelligence agency in Paris, according to the Reuters report. Investigators are trying to figure out whether Merah acted alone or got any help from his brother Abdelkader.

However, DCRI head Bernard Squarcini had told the Le Monde daily on Friday that Merah had acted alone and the brutal killings were not pre-planned. Yet, the investigators now have reasons to suspect Abdelkader's involvement in the brutal killings.

The police union spokesman Michel Crepin told that there was evidence to suggest that Abdelkader Merah had furnished means (and) worked as an accomplice in the incident. However, he declined to elaborate further.

According to a Reuters report quoting the public prosecutor leading the case, police found explosives in a car that Abdelkader owned and the police were aware of Abdelkader's jihadi connections.