MILAN -- Tunisia’s Interior Ministry says police have arrested Anis Amri’s nephew and two others suspected of belonging to the same extremist network.

The ministry says in a statement that Amri - suspected of driving a truck into a Christmas market crowd in Berlin, killing 12 - had sent his 18-year-old nephew Fedi money to join him in Europe.

It is unclear whether the suspects helped Amri flee Berlin.

The nephew was arrested in Amri’s hometown of Oueslatia while the others were arrested in Tunis. The arrests occurred Saturday.

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Earlier, Spain’s Interior Minister said police are investigating whether Amri was in contact with another possible extremist in Spain.

Interior Minister Juan Ignacio Zoido tells Spanish radio station Cope that Spanish police are looking into a tip passed on by German authorities that Amri had developed a contact in Spain.

Zoido says “we are studying all possible connections (between Amri) and our country, above all with one specific person.”

On Monday, Amri’s fingerprints and wallet were found in a truck that plowed into a Christmas market in Berlin, killing 12 people and injuring 56 others. After fleeing from Germany and through France, he was shot dead by Italian police in Milan on Friday.

ISIS has claimed responsibility for Monday’s attack.

Sources confirmed to CBS News on Thursday that Anis Amri was placed on the U.S. no-fly list in July of this year, after German authorities advised he was under investigation for links to terrorism.

Meanwhile, a casket containing the body of the Italian victim of the truck attack arrived in Rome.

The body of Fabrizia di Lorenzo, 31, arrived at Rome’s Ciampino airport at midday, five days after she was killed with 11 others. Italian President Sergio Mattarella was on hand for the arrival.

Di Lorenzo had been living in Berlin and went to the Christmas market to buy presents to celebrate the holiday with family in her hometown of Sulmona, in central Italy.