Hong Kong’s deadliest fire in decades is raising questions about corruption and negligence in the renovations of the apartment complex where at least 128 people died.

In just a few short hours on Wednesday afternoon, what began as a small fire on the first floor of an apartment building swelled into a raging inferno that consumed seven high-rise towers on a Hong Kong public housing estate.

Authorities have said that sticking styrofoam boards to windows during the Wang Fuk Court renovations had worsened the blaze. They believe the materials were not up to safety standards and have arrested three men connected to the renovations on suspicion of manslaughter. The contractor could not be reached for comment.