A Paris court rejected an appeal on Wednesday to release four Frenchmen who are under formal investigation in France after being released last week from the US naval base in Guantanamo Bay in Cuba.
The court upheld a ruling by another French court on Monday that the men could not be released because there was a risk they could flee, cause disorder or talk to each other. The appeal will be heard again next week.
The men are being held on suspicion of "associating with criminals engaged in a terrorist enterprise".
Interior Minister Dominique de Villepin called for a thorough investigation into whether the four had any links to terror attacks.
"It is very important to ask all the questions that the French people are asking themselves. What links with terrorist groups? What participation in, or association with this or that attack?" Villepin told RTL radio just before the appeal was rejected.
"I think it's important to do everything to find the truth," he added.
Nizar Sassi, Mourad Benchellali, Imad Kanouni, and Brahim Yadel were captured during the US-led war in Afghanistan late in 2001 and held by American forces on suspicion of fighting for the ousted Taleban regime. They returned to France on July 27.
The Paris court's president, Monique Radenne, rejected the appeal to release the men under rules which allowed her only to free them if a mistake had been made in the investigation, or if there was evidence of obvious misconduct.
Three judges from the same court were due to examine the appeal more thoroughly next Monday.
"This (Wednesday's) decision does not prejudge what will be decided at the in-depth hearing," said Jean-Baptiste Rozes, Yadel's lawyer.
Wednesday's ruling was "one stage in the case but decisive stages are still to come" said William Bourdon, lawyer for Benchellali and Sassi.
Several lawyers for the men say they suspect their detention in France shows Paris is using the case to improve ties with Washington that were strained by its opposition to the Iraq war.
President Jacques Chirac has said French justice must determine the men's innocence or guilt. Three other Frenchmen remain in detention at Guantanamo.
Five Britons released from the US base in March were freed within a day by British police without charges. A Danish citizen released this year now also lives as a free man.