An improvised explosive device was discovered on a bus carrying Bulgarians in the Hungarian capital Budapest on Sunday afternoon.
The device was found in unattended luggage which aroused suspicion after emitting a strange smell.
It was reported by local media sources that the owner of the suitcase, believed to be a Czech or Slovak national, boarded the bus at its departure point in Prague, Czech Republic, before leaving the luggage behind in Brno.
A bomb squad was quickly called to the scene who found the luggage contained a petrol canister and an explosive.
The passengers, who were travelling to the Bulgarian city of Varna, arrived at their destination on Monday morning after being transferred to a different bus.