Austrian police have arrested 15 people accused of being part of a criminal group that made €2.5 million ($2.8 million) for smuggling 700 migrants into the country.

The group allegedly drove the migrants from the Serbian-Hungarian border to the north of Vienna from where they could travel onward to Germany.

How were the smugglers discovered?

Austrian authorities first opened an investigation into the criminal network last month.

Police said they arrested the 15 smugglers on November 16 when 25 vehicles carrying 200 to 300 migrants were intercepted in vehicle checks in Lower Austria and at a Vienna hotel. Police seized 14 vehicles in the operation.

The investigation found the ring removed the back seats and sprayed over the back windows to conceal the 12 to 15 people they carried in each car or van.

Drivers were recruited in Moldova, Ukraine, and Uzbekistan through social media ads offering up to €3,000 (about $4,000) in monthly wages. The drivers were all said to have tried to escape upon capture.

The Syrian, Lebanese and Egyptian migrants each paid €4,000-€5,000 (about $4,500 to $5,600) to be driven from the Serbian-Hungarian border through Slovakia and the Czech Republic to northeastern Austria.

Where did the migrants want to go?

Most of the migrants said they intended to then travel to Germany.

A third of them decided to apply for asylum in Austria, police spokesman Johann Baumschlager told the German press agency. The rest had probably traveled to Germany already, he added.

The EU introduced a new migration pact in October that tightens up on illegal entry into the bloc while allowing skilled workers greater access to the job market.

Authorities have arrested over 330 people for trafficking people in Austria this year.

jc/rc (AP, dpa)