By Greg Botelho, Jethro Mullen and Karl Penhaul
CATANIA, Italy (CNN) -- The captain of a ship full of migrants that capsized in the Mediterranean Sea has been arrested on suspicion of "reckless shipwreck, multiple manslaughter (and) abetting clandestine immigration" for his role in a disaster that left hundreds dead, an Italian prosecutor's office said Tuesday.
Mohammed Ali Malek, the 27-year-old captain from Tunisia, faces the same prospective charges as one of his crew members, 26-year-old Mahmud Bikhit of Syria, according to a news release from the prosecutor's office in the Sicilian city of Catania.
Authorities there plan to ask a judge Tuesday to keep both men jailed as the case against them continues.
Malek may have caused his ship's capsizing late Saturday when he erred in his navigation, leading his vessel to collide with a merchant ship that had come to help, according to the release from the Catania office, which is headed by prosecutor Giovanni Salvi.
That's one of two possible causes that investigators have considered, the other being that the migrant ship tipped over after everyone ran to one side of it.
There's no indication that the King Jacob cargo ship, which went to the aid of the migrant boat, had anything to do with its sinking. To the contrary, Salvi's office said the vessel "dutifully provided relief (and) did not contribute in any way to the fatal event."
"Only the commander of the fishing vessel and its crew are suspected of causing the crime," the Catania prosecutor's office said.
20-meter boat had about 850 aboard
This revelation comes hours after a U.N. official said the King Jacob could have caused the other vessel's capsizing either by touching it or by producing a big wave that led it to tip.
Those were two of three possibilities outlined by Carlotta Asami, a spokeswoman for the United Nations refugee agency, to CNN early Tuesday. The other was that the 20-meter (66-foot) boat was simply too overcrowded, with about 850 people packed aboard.
Mark Clark, a communications executive representing OSM Maritime Group, the company that manages the King Jacob, denied the cargo ship caused the migrant boat to capsize. He said he believed that people on the migrant boat rushed to one side, causing many to fall off.
The cargo ship was going very slowly as it approached, hardly making any waves, Clark told CNN. It deployed rescue boats, a gangway, nets and life rings, he said.
The King Jacob, whose crew members are all from the Philippines, saved 22 of the survivors, Clark said.
Italian authorities have said that in all, 28 people were rescued.
That leaves hundreds more presumed dead.
Locked in lower part of the ship, survivor says
Asami said their accounts made it "credible to think" that between 800 and 850 people were on board the boat that capsized roughly 110 kilometers (70 miles) north of Libya.
Many of the victims are feared to be still inside the sunken boat.
Asami said the survivors told her and her colleagues that they were all on the highest part of the overcrowded boat, while many people were down in the lowest area.
Italian authorities said Sunday that an unidentified Bangladeshi survivor had told them that smugglers had locked many people inside the lower levels of the vessel.
According to the Catania prosecutor's office, these lower compartments flooded immediately.
Mediterranean migrant deaths skyrocket
The likely toll makes the sinking the deadliest known disaster involving migrants crossing the Mediterranean from North Africa. It's part of a larger problem of people putting their lives in the hands of human traffickers, feeling that's a better option than the despair they're leaving behind.
And it's getting worse.
At least 1,776 people have died or gone missing so far in 2015 in the sea that touches Europe, North Africa and parts of the Middle East, according to the U.N. refugee agency.
By comparison, some 96 people had died in the Mediterranean at this point last year.
Some 36,390 people have managed to safely reach Italy, Greece or Malta in the first few months of 2015, UNHCR spokeswoman Melissa Fleming tweeted Tuesday.
More Syrians -- nearly 9,000 -- are taking to boats to find refuge than citizens of any other country, something that's perhaps not surprising given that country's ongoing civil war.
The other countries where the most migrants have come from are Eritrea, Somalia, Afghanistan and Nigeria.
Ship owners' warning
Shipping companies recently warned that European governments are putting what they say is an unfair burden on their vessels to go to the aid of migrant boats in trouble.
"We believe it is unacceptable that the international community is increasingly relying on merchant ships and seafarers to undertake more and more large-scale rescues, with single ships having to rescue as many 500 people at a time," the European Community Shipowners Associations said in a letter to EU leaders last month.
"Commercial ships are not equipped to undertake such large-scale rescues, which also create serious risks to the safety, health and welfare of ships' crews who should not be expected to deal which such situations," the letter said.
Commercial ships rescued more than 40,000 people in the Mediterranean last year, according to the International Organization for Migration. That's higher than the more than 35,000 people saved by the Italian coast guard but lower than the 80,000 rescued by the Italian navy, which was running a special program, Mare Nostrum, for most of the year.
EU vows to fight traffickers
European Union ministers met Monday in Luxembourg and proposed a 10-point plan to help address the crisis.
"We are not yet working on numbers, but what we have agreed on today is, for sure, the need to increase significantly the resources at sea, and the level of the operation, doing more search and rescue and doing it more together," said Federica Mogherini, the EU high representative for foreign affairs and security policy.
Mogherini told CNN that the European Union must fight human traffickers, strengthen Europeans' duty to save lives at sea and share responsibility when it comes to the resettlement and relocation of refugees.
"We need to fight the organizations that are trafficking and smuggling people, so that we can prevent desperate people from leaving in desperate conditions," Mogherini said. "My pain is that it was a reaction coming too late after so many people died."
But some groups said European officials were offering too little too late.
"What we needed from EU foreign ministers today was life-saving action, but they dithered," said Justin Forsyth, the chief executive of Save The Children.
"With each day we delay we lose more innocent lives and Europe slips further into an immoral abyss," Forsyth said in a statement. "Right now, people desperately seeking a better life are drowning in politics."
CNN's Karl Penhaul reported from Italy, Jethro Mullen from Hong Kong and Greg Botelho from Atlanta. CNN's Hada Messia, Isa Soares, Atika Shubert and journalist Barbie Nadeau contributed to this report.
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