PORTLAND, Ore. -- For the second time in two days, a Northwest Portland homeless camp was discovered on fire.

The second fire at Northwest 19th Avenue and Thurman Street occurred Friday evening, less than 48 hours after an early morning fire at the camp Thursday.

Investigators have not determined how each fire started.

It is not known if anyone was hurt in the second fire. No one appeared to be injured from the first fire.

Portland Fire & Rescue investigators said they have begun to look into the possibility of arson in connection with the recent string of homeless camp fires. Officials on Thursday said there have been 15-20 fires at homeless camps over the last two months.