Italian prosecutors have ordered the seizure of a migrant rescue ship and accused the aid group Doctors Without Borders of illegally disposing of 24 metric tons (26.5 tons) of medical and contaminated waste accumulated during nearly 50 rescues.

Prosecutors in Catania, Sicily said Tuesday that 24 people were under investigation, including the aid group’s Italy personnel and the crew of the Aquarius. Prosecutors accused them of working with a Sicily-based shipping company to mix medical and “contaminated” waste, like migrants’ clothing, with other garbage to save money.

Prosecutors ordered the sequester of the Aquarius, which is currently moored in Marseille, France, as well as the seizure of 460,000 euros ($526,000), which prosecutors said was the amount saved by the group by not properly disposing of the material.

Doctors Without Borders called the accusation “disproportionate” and another attempt to criminalize migrant rescues. The group, known by its French acronym MSF, said its waste disposal followed all approved “standard procedures.”

At the same time, however, MSF allowed that there may have been lapses, especially among port authorities with whom MSF worked, acknowledging prosecutor video showing latex gloves and what appeared to be a syringe mixed in with regular garbage.

“We are ready to clarify the facts and respond about the procedures we followed, but we strongly reaffirm the legitimacy and the legality of our humanitarian activities,” said MSF Italia’s director general, Gabriele Eminente.

At a news conference, MSF officials expressed shock at the prosecutors’ claim that migrants’ clothing alone could spread infectious disease, saying it showed ignorance about public health and was more an attempt to tarnish MSF’s reputation.

The Aquarius, a 77-meter (252.62-foot) -long former fishery protection vessel, is perhaps best known for having become a pawn in the European battle over migration in June after Italy’s new populist government refused to let it dock in an Italian port.

After a weeklong standoff at sea that returned the migration debate to the world stage, Spain agreed to let the Aquarius dock with its 630 migrants who, along with tens of thousands of other migrants before them, had set off from Libya aboard smugglers boats.

The same Sicily prosecutors’ office behind the new investigation made headlines in 2017 when it publicly accused rescue groups of aiding illegal migration by being in contact with Libyan-based human traffickers as they plucked migrants from the sea off Libya’s coast. To date, the investigation hasn’t produced any indictments.

In the new probe, dubbed “Operation Borderless,” prosecutors alleged that between Jan. 1, 2017, and May 2018, MSF and the Sicily-based Mediterranean Shipping Agency knowingly avoided the “rigid treatment” required for “dangerous waste,” including food containers and medical equipment used on board the ship to treat sick migrants.

Prosecutors produced documentation filled out by the suspects that certified that no medical waste or contagious or infections substances were being thrown away. Prosecutors also provided wiretaps of communications between MSF personnel and the shipping agency about how to classify the material.

A statement from prosecutors noted cases of scabies, HIV, tuberculosis and meningitis among newly arrived migrants and said their “contaminated clothing” risked spreading infection.

They accused the suspects of “organized activity trafficking in illegal waste.”

Another aid group that works with MSF aboard the Aquarius, SOS Mediterranee, denounced the ship’s sequester as a “politically driven attack” and urged French authorities to “show restraint” as they weigh the seizure order from Italian prosecutors.

Italy’s hard-line interior minister, Matteo Salvini, who drove the June crackdown on the Aquarius and other aid groups, praised the Catania prosecutors for the new investigation, which also involved another rescue ship the Vos Prudence.

“I did the right thing by blocking the NGO ships, for not only stopping the traffic of clandestine migrants but also, apparently, the traffic in toxic waste,” he tweeted with the hashtag (hash)portsclosed.