Suspected Islamist militants arrested in France were plotting to kidnap a Jewish judge, sources close to the investigation told French media.
Of the 19 people arrested across the country on Friday, 16 remain in custody and the first court hearings are due to be held shortly.
France expelled two foreign-born radical Islamists on Monday.
An Islamist gunman, Mohamed Merah, killed seven people in south-western France last month before being shot.
A lawyer for his Algerian father says she has evidence his son pleaded his innocence in talks with police besieging his flat in Toulouse.
A French police source suggested the allegation did not square with the facts of the siege.
Sources close to the investigation told French media that some of the suspects seized in Friday's dawn raids had been planning to kidnap Jewish magistrate Albert Levy in the eastern city of Lyon.
Mr Levy and his family are now under police protection.
The head of France's Central Directorate for Domestic Intelligence (DCRI), Bernard Squarcini, said earlier that the suspects were French nationals involved in "collective war-like training, linked to a violent, religious indoctrination".
Some belonged to a banned extremist group, Forsane Alizza, and had been involved in paintball gun games, he added.
Police also seized a number of weapons including four Kalashnikov rifles, eight other rifles and "seven or eight" handguns, along with tear gas canisters and a taser, Mr Squarcini said.
French anti-terrorism legislation allows for suspects to be held for four days, and some of the suspects may be charged on Tuesday.
Right to appeal
On Monday, the French interior ministry announced two men had been expelled on grounds of state security and public safety, and had returned to their countries of origin.
One of these, Malian imam Almany Baradji, had reportedly preached anti-Semitism and advocated the full face veil for women - which is illegal in France.
The other, Algerian national Ali Belhadad, had already served a prison sentence for his role in a 1994 attack in Morocco, and had renewed his "ties with the radical Islamist movement in recent weeks".
Both men may appeal against their expulsion, the French interior ministry told the BBC News website on Tuesday.
They had not been allowed to make appeals earlier because their expulsion was an "urgent procedure".
Two imams from Saudi Arabia and Turkey and a suspected Tunisian militant are similarly expected to be expelled, with more expulsions to follow, officials said.
'I am innocent'
According to the French authorities, Mohamed Merah confessed to three gun attacks in which he killed unarmed three soldiers, and three small children and a teacher at a Jewish school.
One soldier and a schoolboy were also seriously injured in the point-blank attacks, which Merah apparently filmed with a camera strapped to his chest.
Days after the final attack, he was surrounded at his flat and shot dead after a 30-hour siege as he reportedly fired on police.
Zahia Mokhtari, a lawyer for Merah's father, told France's BFM television on Monday she had two identical videos of Merah that contradict police accounts of the siege.
"In these videos, he says, 'I am innocent. Why are you killing me? I didn't do anything,"' she said.
She would not say how she had obtained the videos, saying she would reveal more on their origin once she had filed a lawsuit in French courts against RAID, the elite police unit involved in the siege.
However, a police official with knowledge of the investigation pointed out to AFP that Merah had led police to evidence that proved he was the perpetrator.
During conversations with police, the French authorities say, he told them where to find the video he took of the killings.
The source who spoke to AFP said Merah had toyed with police during the stand-off, initially agreeing to surrender but later vowing to "die with his weapons in his hands".
Ms Mokhtari said 10 lawyers, seven of them Algerian and three French, were planning to represent Merah's father, Mohammed Benalal Merah.