(CNN) Amid the ongoing controversy over immigration, the owners of two rescue boats say Italy has forced them to stop operating.

One of the boats, the Lifeline, has 234 people on board whom it rescued off the coast of Libya and 17 crew members. Italy says it will seize the Lifeline for violating international law

The other, the Seefuchs, or Sea Fox, docked in Malta after Italy questioned its registration.

The boats are operated by German nongovernmental organizations. Operators insist they are registered in the Netherlands, which has denied responsibility for them.

Italian Interior Minister Matteo Salvini

Danilo Toninelli, the Italian minister of infrastructures and transport, said on Twitter that the Italian government will sequester the Lifeline and investigate whether it is in violation of international laws.

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