GRASSE, France, July 15 (Reuters) — The French police on Sunday were searching for a convicted killer who made a daring escape from Grasse prison in southeast France with the help of four masked men and a helicopter.

The well-planned breakout late Saturday took only five minutes and was the second time the killer, Pascal Payet, 43, had used a helicopter to escape from jail.

Maurice Barate, a security official at the prison, said the breakout was carried out by four masked men who hijacked a helicopter at nearby Cannes and took the pilot hostage.

They landed on the prison roof at the start of the night shift and used heavy machinery to break open two doors and enter the isolation ward where Mr. Payet was held.