Tourists at two Texas nature reserves have been warned of unhealthy air quality levels on Thursday, according to the U.S. Environmental Protection Agency (EPA).

An air quality map from the EPA’s AirNow website showed an area in south Texas, encompassing both the Laguna Atascosa and Lower Rio Grande Valley National Wildlife Refuges, facing heightened pollution levels.

The warning indicates that conditions could pose health risks for sensitive groups, such as children, the elderly, and individuals with pre-existing respiratory conditions.

This is a breaking story. More to follow.