The latest happened early Monday morning at an empty warehouse on South Brightleaf Boulevard.
Investigators say the half dozen fires set in Smithfield over the past few months all have things in common.
"Most of 'em have For Sale signs in the front yard, there's no power on the house, and that's been the general theme until tonight. This has been a warehouse," explained Lieutenant R.K. Powell with Smithfield Police.
Monday's fire didn't spread far. A Smithfield police officer managed to put it out with a fire extinguisher.
Anyone with information is asked to call Smithfield Police at (919) 934-2121. There's a $5,000 reward.