OMAHA, Neb. (AP) — An investigative report from the State Fire Marshal’s Office says Metropolitan Utilities District workers didn’t mark the natural gas line that was breached and sparked a massive fire that destroyed a building in downtown Omaha.

The report is the basis of a June 23 letter notifying the district that the Marshal’s Office is preparing to conclude that the utility violated state pipeline-safety regulations.

The report says that the underground excavators who hit the pipe while drilling in the area couldn’t have known of its existence without the markings of nearby gas lines.

The district has previously said that it properly marked the lines.

The “notice of probable violation” letter is marked “draft.” Both the district and the Marshal’s Office say the investigation is continuing.