BESANCON, France — A Chilean man was order jailed in eastern France on Friday while he is investigated in the disappearance nearly four years ago of his ex-girlfriend, a Japanese student, in a case of suspected murder spanning continents but in which the body has not been found.

Nicolas Zepeda, 29, extradited from Chile earlier in the day, was ordered detained by a judge in Besancon after hours of deliberation.

The prosecutor in Besancon, where the missing Narumi Kurosaki had been studying, said the extradition of the suspect by Chile was a "new start" for the investigation even though Zepeda refused to answer questions of the investigating judge.

"He simply declared that he is innocent" and expressed hope the real killer would be found, prosecutor Etienne Manteau told reporters.

Being placed under investigation is a step short of formally being charged, under French legal procedure. Formal charges would come if the investigating judge concludes there is sufficient evidence to put the suspect on trial.

Manteau predicted a trial could be held next year.

It was a "major advance ... but it's not over," he said of the extradition. He himself had traveled to Chile as part of the murder probe.

The regional press, which has followed the investigation, has described a love affair that allegedly went awry. Zepeda reportedly had met Kurosaki in Japan then traveled to France to see her after she ended the relationship.

With Zepeda in custody, investigators must now plumb the personality of the suspect and "understand who Nicolas Zepeda really is," the prosecutor said.

Kurosaki disappeared in the early hours of Dec. 5, 2016, from her residence at the Besancon university campus. Zepeda had already returned to Chile before her disappearance was investigated.

Despite long searches in the region's thick forests and elsewhere, investigators failed to find her body, but police believe he killed her.

During court proceedings in Chile, Zepeda acknowledged that he had visited Kurosaki at her apartment on the night she disappeared, even though their romantic relationship had ended. He said they had consensual sex.

"We're obviously interested in everything that might be proposed by the defense," the prosecutor said.

Until his extradition, Zepeda had been under house arrest at his mother's apartment in the resort of Viña del Mar, 120 kilometers (75 miles) northwest of Santiago.

Zepeda was turned over to French officials and put on a Paris-bound flight with police escort. From Charles de Gaulle airport, he was transferred Friday by car to Besancon, in the foothills of the Alps. His extradition was approved by Chile's Supreme Court in May, but was delayed because of the coronavirus crisis and the cancellation of many international flights.