On the A21 Vienna ring road a group of 80 migrants were spotted walking along the road at around 8:00 am and risking their lives by attempting to cross it during heavy traffic.
Police spokesman Johann Baumschlager said that they are likely to have been abandoned by people smugglers.
Another group of 60 migrants were found near the same area, and later on Thursday a group of 20.
They are currently being questioned by police. It's believed they were abandoned in the Schwechat area on the S1 road.
Officers also received a call at around 5am that several people had been spotted walking along the train tracks near to Gross-Sierning, St Pölten, but were unable to find them.
At 6.15 am they received another call from Austrian Railways that the group had reached Loosdorf in Melk.
Baumschlager told the ORF broadcaster that the railway line was closed between 6:20 and 6:55, with some delays to train services. Police apprehended 12 people, including 11 Pakistanis and one Indian man, who had made their way into Austria illegally.
In the last few weeks large groups of migrants have been found abandoned in Lower Austria and Baumschlager said it was proving to be a "logistical challenge" for local police who have to be constantly on the lookout around Marchegg, St. Pölten, Bad Deutsch-Altenburg and Schwechat.
Austria is on the main migrant land route into Europe, with thousands
passing through the country after crossing into the European Union over the
Groups of migrants are now stopped almost daily after crossing into Austria.