PARIS — French police detained a 17-year-old who took a class full of preschoolers hostage today, releasing all the children safely after hours of tense negotiations that drew nationwide attention.

“The hostage-taking is over,” Jean-Marc Magda, aide to the mayor of the eastern French city of Besancon, told The Associated Press by telephone. All 20 children who had been taken hostage and their teacher were released safely, he said.

The hostage-taker was detained, and remained inside the school with officers from a specialist police force brought in to deal with the situation, Magda said.

French television showed a wide-eyed girl being draped with a green blanket and carried away from the school. Police and worried families had surrounded the school since early in the day.

The motives of the hostage-taker were unclear.

Besancon Mayor Jean-Louis Fousseret said the teen had been treated for depression but had not taken his medication in recent days.

The hostage-taker initially seized a class of 20 children but released 14 throughout the morning, including one who “more or less escaped,” Fousseret said.

Five or six children and the teacher were believed to be still in the preschool when the officers entered around lunchtime, Fousseret said.

The hostage-taker did not threaten the children and allowed them to go to the bathroom throughout the ordeal, Education Minister Luc Chatel said.

The incident took place at the Charles Fourier preschool in Planoise, a neighborhood of housing projects with a large immigrant population.