Officials in Poland say a 22-year-old student will be questioned on suspicion of having planted a home-made explosive device on a bus and causing injuries to one person when the device went off.

A container filled with nails exploded in the street in the southwestern city of Wroclaw Thursday, after it was carried out of the bus where it had been left. One person was slightly injured.

Police head Jaroslaw Szymczyk said late Tuesday that the suspect, who was detained earlier in the day, is Polish and studies in Wroclaw.

Deputy Prosecutor General Marek Pasionek said the suspect will be questioned on Wednesday on charges of having planned to kill many people.