( CNN ) -- The company that was laying cable before an explosion last week at a popular Kansas City , Missouri , restaurant -- a blast that killed one person and injured at least 15 others -- did not have a permit for the excavation , a city official said Monday . Those who fail to have such a permit could face a $ 500 fine and up to six months in jail , Assistant City Manager Patrick Klein said . The contractor , Heartland Midwest , previously had worked in Kansas City after obtaining proper permits , according to Klein . But he said the company did not do so last Tuesday , when one of their employees laying fiber optic cable hit a 2-inch gas line with an underground boring machine . The explosion occurred about an hour later , just after 6 p.m. CT ( 7 p.m . ET ) . Officials : Contractor for cable company hit gas line . Authorities do not know what caused the leaking gas to ignite , according to Rob Hack , chief operating officer of Missouri Gas Energy . `` But all the damage points to ignition inside the restaurant , '' he said , referring to JJ 's restaurant , a popular place near Country Club Plaza , an area filled with upscale shops and restaurants . The contractor called 911 shortly before 5 p.m. to report the gas-line incident , according to Fire Chief Paul Berardi . Mayor Sly James said city firefighters responded to a call about the gas odor a short time later but left the scene after being told by the utility company that everything was under control . A Missouri Gas Energy employee showed up about 20 minutes after the initial call and , after some initial readings on gas-measuring devices , called for backup , Hack said . The utility 's employees then went into businesses asking people to leave and brought in excavating equipment to try to vent the pipe , according to the Missouri Gas Energy official . But while JJ 's restaurant closed early due to an evident natural gas smell , hostess Deidre Estes and other employees were n't in a rush to leave , unaware of the danger they were in . Then , `` Boom ! And everything was black , '' Estes told CNN affiliate KCTV . `` ... I saw the flames , and I was scared I was going to burn up . And then with all my might , I got this strength and lifted the rubble off . '' The explosion had ripped off the restaurant 's roof , sending flames a few stories high into the night sky . Afterward , debris -- including a destroyed backhoe belonging to the gas company -- was stacked 3- to 4-feet high where the restaurant once stood . CNN 's Steve Almasy contributed to this report .
One person died , others were injured in a blast at a Kansas City , Missouri , plant . The explosion came after a worker laying cable damaged a 2-inch gas line . A city official says the worker 's company did n't have a permit for the work . Those who do such work without permits can get up to 6 months in jail , he said .