An unexploded homemade bomb found on a high-speed rail line to Paris was being examined for clues, French officials said Wednesday.

The small explosive device, made from plastic tubing filed with a mixture of diesel fuel and fertilizer, was found Tuesday on the line linking Paris with a western city, officials said. The bomb's detonator, composed of an alarm clock hooked up to batteries, apparently malfunctioned.

Officials said the device was very rudimentary but could have caused damage.

Police said they were looking into the possibility that the bomb was linked to previous attempts to blackmail French authorities by a mysterious group that called itself AZF.