KANSAS CITY, Mo. (AP) — A nail salon worker accused of starting a fire that killed two Kansas City firefighters is going on trial.

The case against 46-year-old Thu Hong Nguyen will be heard Monday by a judge, not a jury. She is charged with arson, second-degree murder and causing a catastrophe in the October 2015 fire that killed 43-year-old Larry Leggio and 39-year-old John Mesh.

They were trying to quell flames in an area that had been deemed unsafe when a brick wall fell on them. The wall collapse seriously injured two other firefighters. Fire officials subsequently changed safety procedures.

The blaze started in the storeroom of a nail salon that Nguyen was the last person seen leaving. She has pleaded not guilty.