Berlin ? Police arrested a third suspect Friday in connection with a failed attempt to blow up two trains, while Lebanese authorities picked up a fourth man believed to have been involved, officials said.

The man arrested in Germany, whose identity was not released, was detained in the southern city of Konstanz on suspicion of membership in a terrorist organization, attempting to set off an explosion and multiple counts of attempted murder.

Prosecutors said the man was an associate of Youssef Mohamad el Hajdib, one of two Lebanese men accused of planting the bombs July 31.

Meanwhile, Lebanon’s Prosecutor General Saeed Mirza said police in his country detained a 24-year-old man, whom he identified only as H.K.D., on suspicion he was involved in the failed bombing plot.