Three people have been arrested in Hungary in connection with the deaths of 71 migrants found in the back of an abandoned refrigerated truck on Austria’s main highway, police said Friday. The latest migrant tragedy comes as the United Nations’ refugee agency UNHCR announced that the number of Mediterranean migrant crossings into Europe had passed 300,000 this year, up from 219,000 in 2014.

Hans Peter Doskozil, chief of police in eastern Austria's Burgenland province, said that the migrants, including 59 men, eight women and four children, likely suffocated to death, the Associated Press (AP) reported. Authorities reportedly said that a Syrian travel document was found in the truck, indicating that some of the dead were refugees fleeing violence in Syria.

Doskozil said that the three people being held -- believed to be two Bulgarian citizens and one Hungarian national -- would "lead to the perpetrators," who are suspected to be part of a Bulgarian-Hungarian human trafficking operation, according to BBC.

In another migrant tragedy, an estimated 200 people are feared dead after their boats capsized off the Libyan coast Thursday, UNHCR said Friday. Authorities have so far reportedly recovered 82 bodies that washed ashore near the western town of Zuwara.

The two boats were reportedly carrying nearly 500 migrants, of which over 200 have been rescued. The migrants reportedly came from Africa, the Middle East and Asia. About 147 of the rescued migrants have reportedly been sent to a detention facility for undocumented migrants in Sabratha, west of Tripoli.

According to the U.N., over 2,500 migrants have died while trying to cross the Mediterranean Sea this year in rickety and overcrowded boats in their desperate pursuit to enter Europe. In all of 2014, nearly 3,500 people died or were reported missing in the Mediterranean Sea.

"Many of the people arriving by sea in southern Europe, particularly in Greece, come from countries affected by violence and conflict, such as Syria, Iraq and Afghanistan; they are in need of international protection and they are often physically exhausted and psychologically traumatized," UNHCR said, in a statement Friday.