Italian authorities are investigating a local nongovernmental organization (NGO) for allegedly taking money from the Danish shipping firm Maersk after a migrant rescue mission last year, according to reports and the organization, on Tuesday.

Migrant rescue charities operating on the deadly sea route between Libya, Italy and Malta have repeatedly come under scrutiny in Italy, including over alleged collusion with migrant traffickers.

So far, no prosecutor has found sufficient evidence to warrant a trial. But NGO rescue vessels have also repeatedly been impounded by the Italian coastguard over alleged safety issues.

On Tuesday, media reports said that Idra, the parent company of NGO Mediterranea, accepted 125,000 euros ($150,000) from Maersk following a migrant rescue mission in September.

The money was paid after the migrants were rescued from one of the Danish company's freighters after being stranded at sea for more than a month, La Repubblica newspaper said.

Mediterranea's skipper, its head of mission and its owner were placed under investigation for criminal association aimed at abetting illegal immigration and breach of the maritime code, the newspaper said.

The charity confirmed that it had been targeted by a "major police operation" ordered by a prosecutor in Ragusa, Sicily, but dismissed it as part of the prosecutor's "personal crusade" against NGOs.

It said it was being accused of pre-arranging its search and rescue activities "as profit-making schemes," but said the charges were "founded on speculation."

In September, Mediterranea helped resolve an international standoff that left the Maersk Etienne tanker stuck with migrants it rescued but could not take ashore as both Italy and Malta refused to take them in.

The United Nations called for their urgent disembarkation, and the migrants were eventually transferred onto Mediterranea's Mare Jonio ship and taken to Sicily.

A month later, Maersk made the payment to Mediterranea, according to La Repubblica.

The Italian daily quoted the NGO's head of mission, Luca Casarini, as saying that the money had "nothing to do" with migrant rescue activities.

Idra was paid for consultancy work on port management, Casarini added.

Maersk Tankers' press office said the company was aware of the investigation, had not been contacted by Italian authorities, but was "ready to help at any time."

"As the investigation is ongoing, we will refrain, on principle, from commenting further at this time," a company statement added.