German prosecutors said on Wednesday that they have closed their investigation into a bomb attack on Munich’s Oktoberfest in 1980, more than five years after they revived the probe in the hope that new evidence might point to previously unknown co-conspirators.

Thirteen people were killed, including three children, and more than 200 other people were injured in the explosion at the annual beer festival on the evening of September 26.

The dead included the attacker, student Gundolf Koehler, a supporter of a banned far-right group.

The investigation was closed in 1982. But in December 2014, the federal prosecutor’s office said it was looking at the matter again after a previously unknown witness surfaced.

On Wednesday, federal prosecutors said the witness’s indications that there may have been co-conspirators had not been corroborated by the renewed investigation.

They said they had failed to find any other solid evidence that others may have participated as accessories, instigators or accomplices in Koehler’s attack, though that possibility cannot entirely be ruled out.

The investigation also did not support the idea that members of any far-right groups were involved in any criminally relevant way in the attack, prosecutors said, but there is no question mark over Koehler’s own far-right motivation.