Smoke from the Deer Head Fire will be visible today over the Rincon Mountains.

The lightning-caused blaze is being allowed to burn to clear out excess brush and downed trees to help prevent future larger, more intense wildfires.

The fire was surveyed Tuesday with global positioning instruments and has grown to 939 acres, according to a news release from Saguaro National Park.

“Firefighters on the mountain continued to direct the fire’s spread away from important resources in the area, such as the historic Manning Camp,” the news release stated.

The area was already slated for a prescribed burn later this summer when lightning sparked the blaze, Andy Fisher, spokeswoman for Saguaro National Park, previously said.

Wednesday firefighters plan “to use strategic burnouts on the south perimeter between constructed fire lines and the fire” to keep the fire east of Heartbreak Ridge. The activity is expected to produce additional smoke that will be visible in Tucson and eastward along Interstate 10, the news release stated.

More than 30 firefighters are working the blaze.

The Tanque Verde Trail and Juniper Basin Campground are closed.

For additional fire information go to inciweb.nwcg.gov or the Saguaro National Park Facebook page or call the fire information hotline at 733-5150.