Italian prosecutors have ordered the seizure of a migrant rescue ship and accused the aid group Médecins Sans Frontières/Doctors Without Borders of illegally disposing of 24 metric tons (26.4 tons) of medical and contaminated waste accumulated during rescues.

Catania prosecutors said Tuesday 24 people were under investigation, including the aid group’s Italy personnel and the crew of the Aquarius. In a statement, prosecutors accused them of working with a Sicily-based shipping agency to mix “specialized” waste — including medical equipment and migrants’ clothing — with regular garbage to save money.

Prosecutors ordered the immediate sequester of the Aquarius, currently moored in Marseille, as well as of some 460,000 euros ($526,000).

Médecins Sans Frontières/Doctors Without Borders called the decision “disproportionate” and another attempt to criminalize migrant rescues, saying its waste disposal followed all “standard procedures.”