Police have arrested a second person overnight believed to be linked to an attack in southwestern France that led to the deaths of four people, a judicial source says.
Another source said the man, a minor born in 2000, was a friend of the gunman, Redouane Lakdim, 25.
Police arrested a woman connected to the attacker on Friday, a French prosecutor said.
Lakdim, who was initially believed to have acted alone, held up a car, fired on police and seized hostages in a supermarket on Friday, in what President Emmanuel Macron called an act of "Islamist terrorism".
A gendarme who voluntarily took the place of a hostage during the siege has died, France said earlier on Saturday.
'He fell as a hero'
France is in mourning for a French security officer who died from gunshot wounds after voluntarily taking the place of a female hostage during the siege.
Arnaud Beltrame, 44, a gendarme who once served in Iraq, had been raced to hospital fighting for his life after being shot by the gunman during the siege at the Super U store in the southwestern town of Trebes near the Pyrenees mountains.
"He fell as a hero, giving up his life to halt the murderous outfit of a jihadist terrorist," President Emmanuel Macron said in a statement shortly before dawn on Saturday.
The attacker Lakdim was known to authorities for drug-dealing and other petty crimes, but had also been under surveillance by security services in 2016-2017 for links to the radical Salafist movement, Paris prosecutor Francois Molins said on Friday.
The attacker, whose rampage began when he fired on a group of police joggers and also shot the occupants of a car he stole, killed three people and injured 16 others on Friday, according to a government read-out.
Mr Beltrame's death takes the number killed to four.
He was part of a team of gendarmes who were among the first to arrive at the supermarket scene; most of the people in the supermarket escaped after hiding in a cold storage room and then fleeing through an emergency exit.
He offered to trade places with a hostage the attacker was still holding, whereafter he took her place and left his mobile phone on a table, line open. When shots rang out, elite police stormed the building to kill the assailant. Police sources said Mr Beltrame was shot three times.
Police arrested two people after the attack, one of them a woman connected to Lakdim, on Friday and a 17-year-old man said to be one of his friends overnight, judicial sources said.
The Islamic State militant group claimed responsibility for the attack. Mr Macron said security services were checking that claim.
More than 240 people have been killed in France in attacks since 2015 by assailants who either pledged allegiance to Islamic State or were inspired by the ultra hardline group.
France's warplanes have been bombing Islamic State strongholds in Iraq and Syria, where in recent months IS has lost much of a self-proclaimed "caliphate" of territory it seized in 2014.
One multiple attack by Islamist gunmen and suicide bombers killed 130 people in Paris in November 2015 while another killed close to 90 when a man ran a truck into partying crowds in the Riviera seaside city of Nice in July 2016.
Mr Beltrame, who is survived by his wife, was a qualified parachutist who served in Iraq in 2005. He also worked as part of the elite Republican Guard that protects the presidential Elysee Place offices and residence in Paris, Macron said.