PARIS (AP) — The bomb maker for attacks on Paris and Brussels had a previous career as a jailor for the Islamic State group, a lawyer for one of his hostages said Friday.

Belgian authorities say Najim Laachraoui, a 24-year-old Belgian, built the explosive belts used in the assaults on both European capitals and blew himself up at Brussels Airport on March 22. He was also one of several jihadis who held some hostages captured in Syria, according to Marie-Laure Ingouf, who represents two former French captives.

"Laachraoui was one of the jailors of the French ex-hostages, and of other decapitated hostages, as they all shared the same cell," she said in a statement.

Her statement, which also referred to beheaded American captives James Foley and Steven Sotloff, said Laachraoui was known at the time as Abou Idriss and worked alongside Mehdi Nemmouche, a Frenchman who is accused of a 2014 attack on the Brussels Jewish Museum.

Nemmouche had already been previously identified as a jihadi jailor in Syria by one of Ingouf's clients, Nicolas Henin. A message left with Nemmouche's lawyer, Sebastien Courtoy, was not immediately returned.

Ingouf's statement partially confirms reports in French and British media identifying Laachraoui as the man who first imprisoned Foley and British photojournalist John Cantlie and played a key role during negotiations over the fate of Henin and three other French journalists.

All the French journalists including Henin were eventually released. Foley was beheaded in one of the Islamic State group's first gruesome videos, while Cantlie last appeared in a March IS propaganda video. Cantlie's current whereabouts are not known.

Further details about the alleged roles played by Laachraoui or Nemmouche in the captivity of Foley and Sotloff weren't immediately available. Ingouf declined to say anything beyond the statement and her clients did not immediately return messages seeking comment.

Laachraoui, a young mechanical engineering graduate, left for Syria in February 2013 — an early recruit amid a wave of Belgians who have traveled to fight with the extremists there — and later returned home under the alias "Soufiane Kayal."

A central player in the dual attacks that killed a total of 162 people in Brussels and Paris, Laachraoui's job was to make the TATP explosives and the suicide vests used in the assaults. His DNA was found on one of the vests that detonated inside Paris' Bataclan concert hall as well as one that blew up outside France's national stadium on Nov. 13.

The last publicly distributed photograph of Laachraoui shows him pushing a cart full of explosives at Brussels' Airport moments before setting them off.

Lori Hinnant in Paris and John-Thor Dahlburg in Brussels contributed to this report.