(Corrects attribution to teenager picking up stun grenade to La Voix du Nord, not the prefect)
PARIS, Oct 5 (Reuters) - A 15-year-old protesting against France's dilapidated and understaffed schools had his hand blown off on Monday in the northern town of Lens, the local prefect François-Xavier Lauch said.
Local newspaper La Voix du Nord reported that the teenager lost his hand after picking up a police stun grenade.
Lauch said an investigation into the incident had been opened.
(Reporting by Inti Landauro, Editing by Gabriel Stargardter and Richard Lough)
