MILAN — Investigators on Saturday worked to determine if the Berlin Christmas market attacker received any logistical support to cross at least two European borders and evade capture for days before being killed in a police shootout in a Milan suburb.

Tunisian fugitive Anis Amri's fingerprints and wallet were found in a truck that plowed into a Christmas market in Berlin on Monday night, killing 12 people and injuring 56 others.

Despite a Europe-wide manhunt, Amri fled across Germany, into France and then into Italy, traveling at least part of the way by train, before being shot early Friday in a routine police stop outside a deserted train station.

The Islamic State group has claimed responsibility for the Berlin attack, but little is known about any support network backing up the 24-year-old fugitive.

Italian investigators were working to see if Amri had any connections in the Milan area.

Italy was his port of entry into Europe in 2011 and he spent more than three years in Italian jails on Sicily. But an anti-terrorism official said there was no evidence that he had ever been in or around Milan before Friday.

In Tunisia, the Interior Ministry announced the arrest Friday of Amri's nephew and two others suspected of belonging to the same extremist network.

The ministry said Amri, through an alias, had sent his 18-year-old nephew Fedi money to bring him in Europe and join the Abou Walaa network.

The ministry said the nephew told them he was in contact with Amri via Telegram's encrypted communications to avoid detection. He said Amri had recruited him to jihad and asked him to pledge allegiance to the Islamic State, which he did.

The Tunisian prosecutor's office ordered all three held pending further investigation.

In Spain, police were investigating whether Amri was in contact with a possible extremist there, on a tip from German authorities.

“We are studying all possible connections (between Amri) and our country, above all with one specific person,” Interior Minister Juan Ignacio Zoido told Spanish radio.

Italy has found itself at the center of the Berlin attack investigation after the dramatic shootout early Friday that ended the manhunt. The deserted train station and the late hour prompted Italian officers to check the North African man's identity, officials said. Instead of pulling out an identity card, Amri produced a loaded .22-caliber gun, shooting a senior officer in the shoulder before a rookie officer killed him with a single shot.

Amri had arrived in the southern island of Lampedusa illegally in 2011, claiming to be a minor, and landed in jail after setting fire to a migrant center. After he was freed, efforts to deport him failed for bureaucratic reasons.

He reached Germany, where authorities were concerned enough to put him under surveillance for six months this year, ending the operation in September. His request for asylum was refused by Germany in the summer, but the paperwork from Tunisia needed to deport him was delayed for months.

Investigators are looking into why Amri returned to Italy last week as he sought to elude police and whether he had any jihadi contacts in the country.

Authorities were also investigating the apparent coincidence that the truck from a Polish shipping company used in the Berlin attack had been loaded with machinery in the neighboring Milan suburb of Cinisello Balsamo three days before the attack.

Milan police Chief Antonio de Iesu acknowledged the connection was “suggestive.”

On Saturday, Italy welcomed home one of the 12 victims, Fabrizia Di Lorenzo, 31. She had been working in Berlin and was out shopping for Christmas gifts when the truck careened into the market.

A casket containing her body arrived at Rome's Ciampino airport, met by Italian President Sergio Mattarella. Her parents and brother received hugs and condolences.