The Hurst Fire Department is investigating the cause of a structure fire at 7600 block of Precinct Line Rd. that occurred around 8:10 a.m. Dispatched received an EMS call from a male who said his brother was not breathing. When the fire department arrived at the scene, they realized a fire had been in the bedroom and was smoldering. There were two males at the residence; one has been transported to Parkland Hospital and is in critical condition, and the other has no known injuries. The cause of the fire has yet to be determined.