A small number of migrants who were among hundreds rescued in the Mediterranean test positive after tests by Italian authorities.
The shipwreck in the Mediterranean Sea is the first maritime disaster in 2021 involving migrants and refugees seeking better lives in Europe.
A new report from IUCN highlights the scale of the plastic problem in the Mediterranean.
The bloc's foreign policy chief said ministers will agree on sanctions on Belarus on September 21 while EU leaders will discuss restrictive measures on Turkey on September 24.
The Mediterranea NGO said however that Malta has refused them access to a port to disembark the migrants.
Heads of states of France, Greece, Cyprus, Malta, Italy, Spain and Portugal warned Turkey that "unless it ends its unilateral activities", the EU would "develop a list of further restrictive measures".
"The fierce struggle will continue throughout the night to bring the population to safety and protect homes," the fire service said on Twitter.
As they return to the seas for the first time since April, rescue ship operators say migrants fleeing Libya's humanitarian crisis are undeterred by Europe's coronavirus outbreak
News of the missing boat comes amid criticism of the European Union's lack of rescue missions in the Mediterranean Sea.