PARIS, France - Mar 31, 2009 - Hundreds of French workers, angry about proposed layoffs at a Caterpillar office, were holding executives of the company hostage Tuesday, a spokesman for the workers said.

It is at least the third time this month that French workers threatened with cutbacks have blockaded managers in their offices to demand negotiations. Executives were released unharmed in both previous situations.

The latest incident started Tuesday morning at the office of the construction equipment company in the southeastern city of Grenoble.

The workers were angry that Caterpillar had proposed cutting more than 700 jobs and would not negotiate, said Nicolas Benoit, a spokesman for the workers' union.

They did not want to harm the Caterpillar executives, Benoit told CNN.

The workers were inside the Caterpillar building holding five employees, including the head of operations, captive in their offices, Benoit said.

About 500 employees were also outside the building protesting.

CNN could not immediately reach a representative at Caterpillar for comment.

Benoit said the workers were upset that the company did not show up to two earlier scheduled negotiating sessions.

The employees being held in their offices were allowed to get food, Benoit added.

Police arrived at the scene two hours after the incident began but it had not been settled.

Employees at a French 3M factory held a manager hostage for more than 24 hours Wednesday and Thursday of last week over a dispute about terms for laid-off staff.

Luc Rousselet, who was unharmed, was allowed to leave the plant in Pithiviers, central France, early on Thursday morning after talks between unions and officials from 3M France.

Earlier this month, the boss of Sony France was held overnight before workers freed him after he agreed to reopen talks on compensation when the factory closed.

France has been hit by nationwide strikes twice in the past two months.