A day after a predawn fire heavily damaged a Lilburn doctor’s office, investigators are calling it suspicious, though an exact cause isn’t yet clear. Gwinnett County Fire Department officials say they’re still working to determine the cause of the Sunday morning fire at Atlanta GYN-OB, P.C. in Lilburn. Firefighters responded to the blaze around 4:20 a.m. Sunday in response to a call from an alarm company. Firefighters and police found heavy fire in a corner office suite of the commercial office building in the 400 block of Pleasant Hill Road.