BRUSSELS — The Belgian government says there have been attempts to manipulate the investigation into the “Mad Killers” gang that killed 28 people during the 1980s, crimes that remain unsolved to this day.

Belgian Justice Minister Koen Geens told a parliamentary committee Tuesday that in the past “some investigative strategies did not produce adequate results and attempts were made to manipulate the investigation.” He did not elaborate.

Not a single person has been convicted in the killings and the lack of success in the investigation has raised all kinds of conspiracy theories.

Geens’ comments came after a breakthrough into the possible identity of one gang member. The case came to life over the past week with a family report of a deathbed confession of one possible gang member.