* Factory manager released after deal
* Economic crisis raises social tension in France
* French unemployment rising, new data show
(Adds manager's release)
By Mourad Guichard
PITHIVIERS, France, March 26 (Reuters) - Workers at a factory operated by the U.S. firm 3M (MMM) released the French manager they had held hostage for over 24 hours on Thursday after a deal on conditions for laid-off staff.
The industrial director of the group, Luc Rousselet, was barricaded in an office on Tuesday evening and workers had refused to let him out until he agreed to more favourable terms for the 110 employees who face the axe.
"A framework of an agreement allowing for the end of the current crisis on the 3M site in Pithivers was signed today," a union representative said.
Rousselet left his office early on Thursday morning to boos from around 20 workers.
Locking up managers is becoming a tradition in French labour disputes, with police unwilling to intervene to avoid violence.
Earlier this month employees at a Sony factory in southwest France detained the chief executive and human resources director of the Japanese group's French arm overnight and eventually secured better terms for workers facing dismissal.
Unions at the 3M plant in Pithiviers, near Orleans, south of Paris, were demanding more money for departing staff, guarantees for those remaining and payment of salaries for those who went on strike over the redundancy plan.
"In the framework, the managers of 3M have committed to take into account all the social consequence of the restructuring project," the union representative said of the agreement.
Diversified technology group 3M makes everything from cellophane tape to optical films for liquid crystal displays. France is its sixth largest market and it employs 2,800 staff at eight sites, according to the group's website.
"I am among the 110 people laid off and I know that I will not find another job in Pithiviers," said Edwige Ferrage, who had worked at the company for 38 years.
"I would never have imagined finishing my 3M career like that. It hurts. I feel humiliated, like all the workers here."
The company has said it needs to cut jobs at Pithiviers to reduce overcapacity because of falling demand.
"We have had five rounds of negotiations ... and at the end of the last one we reached an agreement on a certain number of points, but there are still measures left where there are substantial points of disagreement," Rousselet said.
On leaving his office, Rousselet said he was satisfied that negotiations had restarted.
Social tensions are rising in France because of the economic crisis. More than two million people are already unemployed and hundreds of thousands more are expected to lose their jobs this year as the recession deepens.
Unemployment jumped by 79,900 in February, a 19.0 percent rise on the year, new figures showed on Wednesday.
Between 1.2 and 3 million people took to the streets of French cities last week to denounce the government's handling of the crisis and workers from a Continental tyre factory facing closure took to the streets of Paris on Wednesday to protest. (Writing by Crispian Balmer and Anna Willard; editing by Michael Roddy)