A massive fire destroyed an apartment complex on the north side early Friday morning and firefighters had a tough time putting it out. The fire broke out around 3 a.m. near Castle Hills. So far, there haven't been any reports of people injured, but several pets have been seen roaming around nearby. Firefighters rushed to the scene south of Loop 410 in the 7900 block of Jackson Keller Road. They said the close proximity of the buildings made fighting the fire more challenging because it spread easily from one building to another. About a dozen apartment units were destroyed, but officials said some of those units were vacant.