Updated

Various murder and smuggling charges will be recommended against one Afghan and seven Bulgarian suspects for the deaths last year of 71 migrants who suffocated in the back of a refrigerated truck found in Austria, Hungarian police said Wednesday.

Zoltan Boross, head of the National Investigation Bureau's anti-illegal migration department, said that international arrest warrants had been issued for three other Bulgarians suspected of being drivers in the Hungary-based smuggling group. The other eight suspects were under preliminary arrest in Hungary.

"We are going to recommend filing murder charges against four people," Boross told reporters. "Regarding the others, we are going to recommend filing charges of human smuggling committed in a criminal organization ... We have the instigators and we have the accomplices."

Boross said some of the suspects had made full confessions, while other denied their involvement.

Migrants from Syria, Iraq and Afghanistan were among those who died in the back of the truck with Hungarian license plates abandoned on the side of the A4 highway between Budapest and Vienna on Aug. 27, 2015.

Boross said experts had determined that the migrants suffered painful deaths by suffocation within three hours after they were locked in the back of the truck.

Boross said the Afghan man considered to be the local boss of the group had been living in Hungary since March 2013 as a recognized refugee and had been involved in smuggling migrants "nearly daily" from Serbia through Hungary to Austria and Germany since at least February 2015.

Boross blamed the suspected ringleader's "unscrupulousness and greed" for the tragedy, evidenced by the fact that a day after the deaths of the 71 migrants, Austrian police found another 67 migrants in a similar truck being smuggled by the same group.

The unidentified Afghan's group had been involved in smuggling at least 1,106 migrants, with part of its revenues forwarded through money transfers to Afghanistan, Boross said.

Robert Crepinko, director of Europol's European Migrant Smuggling Center, said police across Europe were launching 150-200 cases a month investigating human smuggling.

"We are estimating that between 5 to 6 billion euros ($5.5-$6.6 billion) were made in this criminal market in Europe only in the last year," Crepinko said.