The US attorney-general said there were “serious irregularities” at the jail where Jeffrey Epstein died at the weekend while awaiting trial on charges of sex trafficking underage girls.
William Barr said at a conference in New Orleans on Monday that he was “angry” that the Metropolitan Correctional Center in New York had failed to keep Epstein alive.
“We will get to the bottom of what happened and there will be accountability,” said Mr Barr.
His comments came as the fallout over Epstein’s case spread to France, where ministers and campaigners against child trafficking demanded an inquiry.
“The American investigation has brought to light connections with France,” said Marlène Schiappa and Adrien Taquet, junior ministers for women-men equality and for solidarity and health, in a joint statement on Monday.
“It therefore seems to us essential, for the victims, that an investigation be launched in France so that all can be revealed,” they said.
Epstein died on Saturday morning in what the US Department of Justice has called “an apparent suicide”. An autopsy was carried out the next day, but a final determination on the cause of death has not yet been made, said Barbara Underwood, the New York chief medical examiner, in a statement on Sunday.
His death has raised questions about conditions at the MCC, a notorious jail where defence lawyers and defendants have complained for years about the treatment of inmates.
Last month, Epstein was found unresponsive in his cell with marks on his neck. He was placed on suicide watch but had been taken off again at the time of his death, according to a person familiar with the matter.
Prison guards were supposed to check on Epstein every 30 minutes, but that procedure was not followed on the night of his death, according to US media reports. He was being held in the MCC’s special housing unit, a secure area where inmates are kept separate from the general population.
The FBI and the justice department’s inspector-general are investigating the circumstances of Epstein’s death.
The criminal case against Epstein has been short-circuited by his demise, but lawyers representing his alleged victims have vowed to ensure his assets are used to compensate their clients. US prosecutors have vowed to continue to investigate any co-conspirators.
“This case will continue on against anyone who was complicit with Epstein,” said Mr Barr. “Any co-conspirators should not rest easy. The victims deserve justice and they will get it.”
In France, Innocence en Danger, a child protection organisation that campaigns against sexual abuse, called for an inquiry into allegations that underage girls were abused and that some of the perpetrators were French citizens.
“Innocence en Danger has recently received confirmation from a reliable source that several victims of the prostitution ring created by Jeffrey Epstein and his accomplices also have French nationality,” it said.
Epstein kept a luxury apartment on the Avenue Foch in the heart of Paris valued at $8.6m, according to financial disclosures he made in court. An address book said to have been stolen by his butler included the names of several contacts in the French capital.
Homayra Sellier, founder and president of IED, said it was known that French citizens “were involved as very close friends of Mr Epstein” and as victims. “We really have to put pressure on the prosecutor’s office so they open an investigation in France.”
In Paris, the national prosecutors’ office said it was studying the requests for an investigation but had yet to make a decision. Nicole Belloubet, French justice minister, cited the independence of the judiciary and said it was not up to the government to make a decision.
Among Epstein’s associates was his longtime companion Ghislaine Maxwell, who has French as well as US and UK citizenship.
Virginia Roberts Giuffre has alleged in a civil suit that Epstein and Ms Maxwell, who is the daughter of the disgraced publisher Robert Maxwell, used her and other young women as a means to extract favours from and blackmail powerful people. Ms Maxwell has denied the allegations.
Additional reporting by Domitille Alain in Paris