Decades after an attack on an apartment building inhabited by Turkish families in Kempten, Bavaria, the investigations have been restarted.
"An extremist background cannot be ruled out," said a spokesman for the attorney general's office on Friday.
They are investigating murder, but so far have no suspects.
A five-year-old boy died in the fire on the night of November 17, 1990.
The residents of the house were surprised in their sleep and for the most part could only save themselves by jumping out of the windows.
Numerous victims were seriously injured.
The five-year-old was rescued from the burning house by fire fighters, but later died in a hospital.
The residents were people with a Turkish migration background.
Right-wing extremist letter of confession
A letter of confession from then was signed "Anti Kanaken Front Kempten," said the spokesman.
According to the state of the investigation at the time, this group was not known.
In addition, the letter did not contain any perpetrator knowledge.
It was a lead that was followed back then.
The criminal investigation of the time into arson resulting in death remained inconclusive.
There was also no evidence of a "politically motivated act", the police said about ten days after the act.
The letter of confession was only received by a newspaper several days later.
The residents of the house with Turkish roots were suspected at times.
This is reminiscent of the series of murders by the »NSU« terrorist group - even then, the victims' families were at times the focus of the investigation.
The reason for the resumption of the investigation was now press inquiries about the case, said the spokesman for the attorney general.
It emerged that in the vicinity of the crime scene in downtown Kempten »people with a right-wing extremist background« should have lived.
That will now be investigated.
A special commission has been set up and is headed by the Central Office for Combating Extremism and Terrorism of the General Prosecutor's Office.
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jpz / dpa / AFP