The 120-page report said the utility’s workers waited too long before checking whether gas levels had reached unsafe conditions inside JJ’s restaurant on Feb. 19, 2013. An explosion and fire leveled the building, killing Megan Cramer, 46, a server at JJ’s, injuring more than a dozen other people and damaging nearby buildings.

The PSC staff also filed a complaint against MGE asking the full commission to find the utility violated the agency’s safety rules and to authorize the commission’s general counsel to seek penalties in state court.

“They seemed to lack an appropriate sense of urgency given the situation that they found at the site,” PSC staff counsel Kevin Thompson said Thursday. “What we’re basically saying is they failed to implement their own emergency plan.”

The PSC staff report said about a half-hour elapsed between when MGE’s first responders arrived at the scene and when the utility’s personnel first entered the restaurant.

“MGE personnel did not conduct prompt and adequate leak investigations to determine if additional hazards existed and to determine the extent of the hazards in order to make the area safe and to protect life and property,” the report said.

MGE on Thursday disputed the allegations in the report, which the company said did not include “important facts.” MGE also said it would “vigorously challenge” the PSC staff allegations through legal means.

“Upon learning an MGE gas line was damaged by a cable contractor, MGE promptly responded and followed well-established company and industry procedures,” the emailed statement said. “The moment the MGE responder arrived, his investigation began. He called for additional responders, investigated the source of the leak and developed a plan for containing it.

“MGE responders conducted tests and urged the evacuation of several buildings in the impacted area, including JJ’s,” the statement added. “MGE responders urged JJ’s to evacuate on three separate occasions. While many individuals left, our employees cannot force anyone to evacuate.”

The explosion at JJ’s occurred after a crew for Heartland Midwest, an Olathe, Kan.-based cable company subcontractor, breached a natural gas supply line with an underground borer. Fumes from that leak filled the building and were ignited, possibly by a pilot light, according to a Kansas City Fire Department investigation. A little more than an hour passed between the time the leak was reported and when the restaurant erupted in flames.

The U.S. Department of Labor’s Occupational Safety and Health Administration has proposed a $161,000 fine against Heartland Midwest for two willful and three serious violations. Heartland has contested the citations.

The PSC staff report also said there was an unexplained discrepancy in underground utility markings in the area. It said two electrical facilities and one natural gas site were there, but the markings only indicated one electrical site and one natural gas site.

“Had markings on the ground indicated to Heartland Midwest personnel another underground electric facility was present, it is probable that Heartland Midwest personnel would have been able to avoid damaging the natural gas main,” the report said.

MGE has 30 days to respond to the PSC staff report.