EL PASO, Texas -

Hazmat teams responded Tuesday morning to a situation near Doña Ana County Industrial Park at 2500 Airport Road in Santa Teresa, N.M. that occurred shortly after 8 a.m. MDT.

Shortly after 2 p.m. New Mexico State Police requested a civil-support team from the New Mexico National Guard to deploy to the Doña Ana County Industrial Par to assist with monitoring and testing. That team was en route. The Las Cruces Fire Department's Hazmat team was standing by to provide assistance as requested.

Two hundred people were exposed to the unknown substance and were treated at Santa Teresa High School, according to Dona Ana County officials. No one at the school was exposed.

People reported watery eyes, painful throats and respiratory irritation, then feeling sick for about an hour before the evacuation order came.

The Dona Ana County Fire and Emergency Service Department Hazardous Materials Response Team with New Mexico State Police are at the scene.

The Mesilla Valley Regional Dispatch Authority has activated a reverse 911 call to alert residents and businesses within one mile of the incident to remain indoors, seal all doors and windows and turn off air conditioning and heating systems that bring outside air into the home or business.

The Doña Ana County Airport at Santa Teresa was closed to all air traffic and had been evacuated, as well.

The Doña Ana County Emergency Operations Center had been partially activated, with personnel on hand from American Red Cross, New Mexico Environment Department, Doña Ana County Ham Radio Association, the Doña Ana County Public Information Office and the Doña Ana County Office of Emergency Management.