SAN ANTONIO -- The American Red Cross plans to open shelters for residents near a mulch fire in Helotes that is expected to create heavy smoke and ash over the weekend.

Officials said heavy smoke and ash may result from Saturday to Monday because a contracting company plans to aggressively attempt to extinguish the more-than-two-week mulch fire.

Metro Health District Dr. Brian Alsip said a variety of people are at risk of being affected by the smoke and ash.

"People who are at risk are sensitive, meaning they have asthma (or) underlying respiratory conditions," Alsip said. He also said elderly people, pregnant women and children are at risk.

Health district officials said most healthy adults will recover quickly from the smoke exposure, but those experiencing any breathing problems should seek shelter.

Red Cross Disaster Relief official Mac Mcnell said his group is standing by ready to open the shelters.

The Red Cross plans to open shelters at Rawlinson and H.B. Zachry middle schools this weekend to take in people who temporarily want to get away from the smoke.

Officials said 27 families with respiratory problems have been forced to vacate their homes.

North Side Independent School District officials announced on Thursday that three schools will be closed Tuesday due to the mulch fire.

The schools include O'Connor High School and Helotes and Krueger elementaries, said NISD Superintendent John Folks.

The three schools are within a two-mile radius of the fire.