SOUTH BEND — More than a dozen people are lucky to be alive after dangerous levels of carbon monoxide were found this morning in their South Bend apartment building. The deadly gas was discovered after residents of the building in the 200 block of Calvert Street felt sick and went to the hospital. Hospital staff did tests and noticed carbon monoxide levels were elevated and then alerted the fire department. Other residents apartment had no idea they were in danger, until they got a knock on their door. "I am so glad. I really am," Ethel Williams said. "My babies, they survived. We have no problems, no worries. It didn't get into my system." "It can be fatal," said South Bend Battalion Chief David Maenhout of carbon monoxide poisoning. "If it wasn't for us being alerted by Saint Joe Med Center, there could have been more serious injuries, if not fatal, if this would have went on much longer." Williams and 16 others were evacuated from the apartment building about 2:30 a.m. Fire officials said they detected deadly levels of carbon monoxide in parts of the building. "NIPSCO found highly elevated levels of CO, some potentially lethal levels of carbon monoxide," Maenhout said. Williams said she knew something was wrong when she suddenly felt sick. "I started feeling dizzy," she said. "I couldn't sleep. My stomach was hurting. I knew something was wrong, but I just didn't know what it was." She never suspected deadly carbon monoxide gas could be the reason. And had the fire department not shown up, "It would have been different, because I was already having symptoms. So it is good I got out just in time," Williams said. Experts caution others not to ignore the symptoms. The high CO levels were caused by a boiler malfunction, officials said. Safe concentration levels are under 30 parts per million. Levels in the apartment building were showing 100 to 300 parts per million.