The refugee rescue ship "Ocean Viking" is looking for a port to bring 555 migrants rescued from distress ashore.
"We asked all the relevant authorities: Malta, Tunisia, Libya and now Italy," a spokeswoman for the organization SOS Méditerranée told the AFP news agency on Monday.
Malta has already canceled, Tunisia and Libya have not reacted.
"The situation on board is intolerable," said the spokeswoman.
The people suffered from the heavy swell and the oppressive heat.
“Many are seasick.
Some have passed out on deck because of the heat and what they have experienced, "said a member of the medical team on board the" Ocean Viking "in the short message service Twitter.
In several missions in the Mediterranean, aid organizations said they had saved a total of over 800 migrants in distress over the weekend.
According to SOS Méditerranée, the "Ocean Viking" had already brought 196 people on board in four rescue missions by Saturday evening.
On Sunday night, the rescuers came across a wooden boat with over 400 refugees that threatened to sink.
The rescue operation together with the "Sea-Watch 3" and the sailing ship "Nadir" of the rescue organization Resqship lasted all night. The rescue organizations said that the rescued were divided between the "Ocean Viking" and the "Sea-Watch 3". On Sunday, the two ships each had another mission. “We now have a total of 250 guests on board, which our crew takes care of,” explained the crew of the “Sea-Watch 3”.
According to the International Organization for Migration, more than 1,100 migrants have died in the dangerous crossing over the Mediterranean since the beginning of the year. According to official figures, there were more than 1200 fatalities last year. However, experts assume a high number of unreported cases. SOS Méditerranée claims to have saved more than 30,000 people since February 2016.