SAN ANTONIO -- The Texas Commission On Environmental Quality on Friday set up four air quality monitors near the site of a smoldering pile of compost in Helotes.

The monitors will measure the level of soot in the air that is being emitted from the 80-foot high pile that has been burning since Christmas Day.

The monitors were installed at O'Connor High School, Helotes Elementary and at two residential neighborhoods west of the site.

The air will be monitored for at least a week, officials said.

Cameron Lopez of TCEQ said that he doesn't believe that there is any suspicious material in the pile.

"We've known it just to be brush," Lopez said. "Just oak, cedar, elm, materials, tree trunks, limbs -- stuff like that. And we've had no cause to believe there is anything that shouldn't be in that pile."

The monitors will be moved, if necessary, should there be a change in wind direction, Lopez said.

The monitors were installed one day after the San Antonio Metropolitan Health District issued a health advisory for residents who live near the mound.

The health advisory stated that smoke and ash from the fire could create breathing problems for people who have asthma, allergies, lung and heart problems. Pregnant women could also be at risk.

Health officials urged residents to stay indoors, reduce physical activity and reduce sources of indoor air pollutants, such as cigarette smoke, gas, propane, wood burning stoves and furnaces.