An explosion during routine boiler maintenance in the Patrick Gym complex left one University employee with head injuries and an ongoing investigation into the cause of the blast, Burlington asst. fire marshal Tom Middleton said.One of three Physical Plant employees was behind a boiler inspection window when a heavy metal rear access door blew open, director of University communications, Enrique Cordera said.”The employee was standing behind the boiler as the door blew open and it landed on his head,” Cordera said. “He was conscious when transported by UVM rescue to Fletcher Allen.”According to an email sent out to the UVM community stated that he is now in stable condition.The explosion, which happened around 10:30 a.m., created a large bang that sounded like thunder, junior Chris Shackett said.”I was in the room right above the boilers when our desks shook and we heard something that sounded like thunder and lightning,” Shackett said.”I heard the crash of metal hitting the floor,” maintenance specialist Rick DeVoid said. “Then I ran upstairs and called 911 as the area filled with the smell of fuel.”Cordera said that asbestos covered pipes in the boiler room were disturbed by the explosion and state hazardous materials specialists were on their way to take an air sample, assessing the possibility of asbestos air contamination.Burlington fire department and University personnel are making every effort to reduce exposure to the asbestos, which could have travelled into the pool areas, racquetball courts and a Patrick Gym auditorium, Middleton said.Cordera said that the cause of the explosion has yet to be determined.”I’ve taken extensive digital photographs of the scene,” Middleton said. “With these we’ll hopefully determine exactly what happened when the state team arrives.”The University feels there is no reason to believe anyone who was not in the boiler room has been exposed to asbestos, according to a University press release.Middleton said that once he and the state team are satisfied, they will turn the scene over to the University, but it is too soon to tell how long it will take.Portions of the PFG complex are cordoned off, while the majority of the building remains open for use, Cordera said.