ROME (Reuters) - An Italian prosecutor who began an investigation into possible ties between humanitarian organizations that rescue migrants at sea and Libya-based people smugglers said on Wednesday he had no proof of any wrongdoing.

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Carmelo Zuccaro, the chief prosecutor of the Sicilian port city of Catania, previously said he had evidence of phone calls between people smugglers and aid groups, but on Wednesday he said he was expressing only a “hypothesis” and had no proof that could be used in court.

“The ample amount of money that some of the newer NGOs have is an element of suspicion and it is something we are looking into ... No evidence has yet been found” of illicit funding, Zuccaro said. “The profiles of some NGO crew members are not exactly philanthropic.”

Speaking before a parliamentary committee convened to investigate his claims, which he first aired in February when he announced the fact-finding inquiry, Zuccaro asked lawmakers to provide more resources and suggested putting police on ships in the rescue zone.

Without more resources, his office is not able to further the investigation, he said. Information he had collected so far about the activity of non-governmental organization ships came from the EU border agency Frontex, Italy’s navy and coast guard, and the Internet, he said.

Various NGOs have strongly denied all allegations they have colluded with people-smugglers.

Zuccaro has become a divisive figure in Italy’s increasingly heated debate about immigration, which is likely to become a key issue in the national election due by next May. Italy has been left virtually alone to manage hundreds of thousands of migrants who have come by boat from North Africa. More than 1,000 migrants have died this year attempting the passage.

Migrant arrivals are up 30 percent so far this year from 2016, when a record 181,000 came by boat. Because they are no longer moving onto Northern Europe as they did previously, their presence is now more visible in cities and towns across the country.

Border closures by Italy’s European Union partners and more strict identification procedures mean that more of the migrants are choosing to seek asylum in Italy.

Last week, Justice Minister Andrea Orlando said it was “a lie” to paint aid groups as criminals and urged Zuccaro to open a criminal investigation if he had proof of wrongdoing. No such investigation has been opened.

On the other hand, the leaders of the 5-Star Movement, currently polling as the country’s most-popular party, and the anti-immigrant Northern League condemned non-governmental groups for providing a “taxi” service to migrants.

“Our country is not able to take in all migrants -- including the economic migrants,” Zuccaro said, referring to those who do not qualify for asylum.