BERLIN — German prosecutors said Tuesday they are investigating whether three alleged neo-Nazis suspected of a series of racist killings and bombings were also responsible for an earlier explosives attack not previously linked to the group.

If true, the revelation would be embarrassing for German authorities already reeling from a series of blunders in the case of the National Socialist Underground, which is alleged to have killed eight Turks, a Greek and a policewoman between 2000 and 2007. The group also is suspected of carrying out two bombings in which dozens were injured during that period.

The new probe was sparked by a defendant's comments during the trial of the woman said to be the group's sole surviving member, Beate Zschaepe, and four men accused of helping the trio, said Marcus Koehler, a spokesman for the Federal Prosecutors' Office.

Carsten Schultze, one of the co-accused, told a Munich regional court last week that Zschaepe's alleged accomplices, Uwe Mundlos and Uwe Boenhardt, once hinted they were involved in a 1999 bomb attack on a bar run by a Turkish man in Nuremberg.

The attack, in which one woman was injured, had some of the hallmarks of the group's later crimes: it targeted a business run by a member of an ethnic minority; the bomb was hidden in such a way that it would explode when tampered with; and it took place in Nuremberg, where three of the slayings also occurred.

Koehler was unable to say why the 1999 attack hadn't previously been attributed to the group, but said police had now been instructed to investigate whether Zschaepe was involved in the attack, which was being treated as a case of racially motivated attempted murder.

Mundlos and Boenhardt died in an apparent murder-suicide in November 2011 that led authorities to acknowledge the group's existence.

But questions have repeatedly been raised about whether Germany's well-funded security services knew about the NSU before the men's death.

On Tuesday, a police officer told lawmakers in Bavaria's state assembly that the group's name was first mentioned to him in 2007, the dpa news agency reported. Other officers questioned at the hearing challenged this claim.