Austrian security forces on Thursday started searching vehicles for migrants near the border with Italy along the A13 highway, 25 km from the Brenner Pass and also checked goods trains travelling to Austria.
Austrian soldiers and police carried out checks on around 100 vehicles on the A13 including cars, trucks, buses and coaches.
Two women and four men from Ivory Coast and Burkina Faso were found hiding in an empty liquid petroleum gas container wagon on a goods train that had departed from Bolzano.
Austria sent 70 soldiers to its border with Italy last week to help police prevent illegal immigrants from entering through the Brenner Pass amid rising tensions over the number of migrants heading north.
The troop deployment was in response to migrants trying to get across the border by hiding beneath trucks, said senior police official Helmut Tomac and Herbert Bauer of the Austrian army.
Austria, Denmark, Germany, Norway, and Sweden have had a green light from the European Commission to impose temporary border checks despite being part of Schengen, the passport-free travel zone in Europe.
The military deployment is part of a wider EU migrant crackdown, including on its external borders.
Bulgaria said the EU should defend its borders by “force of arms” and announced it would send 600 soldiers to stop migrants crossing from Turkey.