BERLIN - The prime suspect sought in the deadly attack on a Berlin Christmas market - a 24-year-old Tunisian migrant - was the subject of a terrorism probe in Germany earlier this year and was not deported even though his asylum bid was rejected, a senior official said Wednesday.

The suspect - who went by numerous aliases but was identified by German authorities as Anis Amri - became the subject of a national manhunt after investigators discovered a wallet with his identity documents in the truck used in Monday's attack that left 12 dead, two law enforcement officials told the Washington Post.

Meanwhile, a clearer portrait of the suspect emerged, including accusations that he had contact with a prominent Islamic State recruiter in Germany.

German authorities issued a $100,000 reward for information leading to his capture, warning citizens not to approach the 5-foot-8, 165-pound Amri, whom they described as "violent and armed."

His record further deepened the political fallout from Monday's bloodshed - pointing to flaws in the German deportation system and putting a harsh light on Chancellor Angela Merkel's humanitarian bid to open the nation's doors to nearly one million asylum-seekers last year.

Although the vast majority of those who flooded into Europe were on the move to escape war and unrest, dozens of terrorism suspects have slipped into Germany and neighboring nations posing as migrants. Amri, officials said, was not part of the surge of migrants who entered Europe via the onetime main route from Turkey and Greece - a path that has been now largely cut off.

Rather, he came to Germany last year via Italy, where he apparently had entered as early as 2012. He applied for German asylum but was rejected in June and later faced deportation.

Amri had been the subject of a terrorism probe on suspicion of "preparing a serious act of violent subversion," and he had known links to Islamist extremists, authorities said.

Why a failed asylum-seeker with such links and no passport was walking German streets is "the question 82 million Germans probably want an answer to," said Rainer Wendt, chairman of the German Police Union.

The dragnet for the suspect appeared to initially focus on the German state of North Rhine-Westphalia as well as Berlin, both places where he once lived. Police units were due to stage raids, but they remained mysteriously on hold.

The interior minister in North Rhine-Westphalia, Ralf Jager, said the Tunisian man had bounced around Germany since arriving in July 2015, living in the southern city of Freiburg and later in Berlin.

Although authorities have sought to accelerate the deportation of rejected asylum-seekers this year, there is still a backlog in Germany of tens of thousands, many of whom are able to resist because their countries of origin refuse to take them back. Amri, Jager said, was one of them.

Amri had not been deported because - like many asylum-seekers in Germany - he did not have a passport. The Tunisian government, Jager explained, initially denied that he was a national and delayed issuing his passport. Pending his deportation, Amri had received a "toleration" status from the government.

Amri's new Tunisian passport, Jager said, finally arrived Wednesday.

"I don't want to comment further on that circumstance," said a visibly angered Jager.

Authorities knew that Amri had "interacted" with Abu Walaa, a 32-year-old of Iraqi descent arrested in November on charges of recruiting and sending fighters from Germany to the Islamic State. Key evidence in Walaa's case came from an Islamic State defector who had returned to Germany and accused Walaa of helping to recruit him and arrange his travel to Syria.

"Anis Amri was engaging with extremist salafist circles in Germany," a German security official said.

According to Karen Muller, spokeswoman for the Berlin prosecutor, Amri had also been under police surveillance for several months until September of this year, because he was suspected of planning a burglary in Berlin to finance the purchase of weapons. The suspicion wasn't confirmed. He was, she said, found only to be a small-time drug dealer, and surveillance measures were called off in September.

The leaking of the suspect's name and photograph in the press, authorities said, may have upset attempts to find him. Germany's interior minister, Thomas de Maizière, would tell reporters in Berlin only that Germany had registered "a suspect" as wanted on European databases. He refused to give further details.

The two German law enforcement officials, who spoke on the condition of anonymity to discuss a sensitive case, said investigators discovered the man's documents in the cabin of the truck that barreled into the market.

It remained unclear whether officials believe Amri drove the truck.

Revelation of his background seemed set to damage Merkel, who is running for reelection next year.

"There is a connection between the refugee crisis and the heightened terror threat in Germany," said Stefan Mayer, parliamentary spokesman on domestic affairs for the Christian Social Union party.