At 1020am Conroe Fire Department was dispatched to a reported fire at the Salt Grass Steak Restaurant on I-45 North. Fire units arrived to find heavy smoke conditions. A second alarm was called for bringing ESD #1 and Montgomery Fire Departments. Once inside firefighters had heavy fire in the attic area and near the vent hood area. It is unknown as to the cause of the blaze. Just over 20 employees were inside at the time preparing for the noon lunch. One firefighter suffered dehydration. I-45 Northbound feeder between SH 105 and Wilson Road.