The migrants were picked up by the Diciotti coastguard ship on the night of August 15 and were left stranded at sea for 10 days as Salvini refused to allow the vessel to dock in an Italian port.
Salvini, head of the far-right League party, finally relented after Ireland, Albania and the Italian Catholic church agreed to lake most of them in.
Reacting to the disappearance of 50 of those taken in, Giorgia Meloni -- leader of the far-right Brothers of Italy party -- asked on Twitter who would be responsible if one of them committed a crime in Italy, calling for an end to "uncontrolled immigration" and an immediate naval blockade.
Most of those aboard the Diciotti were Eritreans, along with a small number of Somalians, Syrians, Sudanese and Comorans.
Since the start of the year, 3,000 migrants from the former Italian colony of Eritrea have arrived in Italy but less than a thousand have applied for asylum, according to interior ministry figures.
Many Eritreans prefer to continue by land to Germany, Sweden or Britain, despite the heavy controls encountered at the French, Swiss and Austrian borders as well as the EU's Dublin regulation under which a migrant can only make an asylum claim in the first European country the reach.
Meanwhile in Spain the bodies of five migrants were recovered off the southern coast, according to emergency services who also rescued around 500 others on Wednesday .
A spokesman told AFP that the bodies of four men and a woman were picked up during an operation to save a vessel in difficulty in the Mediterranean between Spain and Morocco.
According to the International Organization for Migration more than 28,500 migrants have arrived by sea in Spain this year, while another 313 have perished attempting to make the crossing.