The cars were both found at the railway station. One was earlier towed away to Leighton Buzzard to be examined. A 100-yard cordon was placed around the other one and a series of four controlled explosions were carried out.
The other areas affected included the bus station, part of the Luton University campus and a number of privately owned buildings.
Yesterday's operation at Luton caused serious disruption to rail services after the station was closed at 2.45pm on safety grounds.
Trains were also prevented from passing through Luton until a safety assessment had been completed.
Midland Mainline's northbound trains from London were unable to leave St Pancras station and evening rush-hour passengers faced difficult journeys home.