BRUSSELS - Belgian prosecutors appealed to the public Monday for information about a man who allegedly traveled to Hungary last year with a top suspect in the Paris attacks.

The federal prosecutor's office said in a statement they are seeking details about 24-year-old Najim Laachraoui, who is said to have traveled to Syria in February 2013. It said Laachraoui was checked by guards at the Austria-Hungary border while driving in a Mercedes with Salah Abdeslam and one other person.

Laachraoui is said to have rented a house under the name of Soufiane Kayal in the Belgian town of Auvelais that was allegedly used as a safe house. Prosecutors said traces of his DNA were found there.

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Laachraoui is "someone who must explain himself," Belgian prosecutor Frederic Van Leeuw, stressing that "clues" do not amount to proof.

Investigators have been working on numerous pieces of the puzzle in the many-tentacled Paris attacks case.

"We are far from putting the puzzle together," said Van Leeuw.

Anti-terrorism prosecutors in Belgium and France have worked non-stop on hundreds of cases - 325 cases last year in Belgium and near 60 new cases so far this year, Van Leeuw said.

His French counterpart, Francois Molins, who was also at the news conference, said his team has 244 anti-terror cases in progress concerning 772 individuals either charged or sought.

"(It's clear) we have a general threat," Van Leeuw said.

Abdeslam has a court hearing on Wednesday. France has requested his extradition but Abdeslam's lawyer says his client will fight the request.

Authorities do not know the "exact path" taken by Abdeslam, who had crisscrossed Europe ahead of the Nov. 13 bloodbath then fled the scene, Van Leeuw said Monday.

Abdeslam, suspected as a logistician in the attacks that killed 130 people, was arrested Friday after a four-month manhunt in the same neighborhood in Brussels where he grew up.

Van Leeuw told reporters at a news conference in Brussels that investigators hope to find out the details of Abdeslam's actions between the Nov. 13 attacks and his arrest, "if he decides to tell us."

Abdeslam, 26, a French citizen who grew up in Brussels' heavily immigrant Molenbeek neighborhood, slipped through police fingers on multiple occasions, including the day after the attacks. He was interviewed three times Saturday, the day after his capture - once by prosecutors and twice by an investigating judge - and "wasn't in great shape" because he had been shot in the leg by police during his capture, Van Leeuw said.

Other people are still on investigators' wanted list.

Belgian Foreign Minister Didier Reynders revealed over the weekend that Abdeslam may have been planning further attacks.

"It's maybe the reality, because (as) I said, we have found a lot of weapons, heavy weapons," Reynders said in response to a question from CBS Radio News correspondent Cami McCormick.