Clouds of black smoke hanging over La Porte were visible for miles Monday after a fire erupted from a natural gas liquids pipeline, sparking fears about air pollution spewing from the blaze.

Harris County Pollution Control Services responded to the fire in the 8700 block of Spencer Highway late Monday morning, after the La Porte Fire Department's 9:55 a.m. arrival at the scene. The county department checked the air quality near the fire with mobile monitoring equipment throughout the day.

Pollution control officials said in an afternoon statement that soot levels from the fire were "moderate and not an immediate risk for healthy populations," though "sensitive populations may want to take precautions."

Soot, also known as particulate matter, is composed of fine particles that can irritate the eyes, nose, and throat. Particulate matter can also worsen existing lung conditions and increase the risk of heart attacks and strokes.

LIVE UPDATES: Major pipeline fire erupts in La Porte, prompting road closure and shelter-in-place warnings

The county department pointed residents to its online dashboard offering data from mobile monitoring stations they set up around the site of the fire.

The pipeline, owned by Dallas company Energy Transfer, also affected neighboring Deer Park. It caught on fire at a valve station along Spencer Highway.

Company officials said in a statement Monday afternoon that the fire continued into the afternoon since the stretch of pipeline had to be "isolated so that the residual product in the line can safely burn itself out."

The La Porte Fire Department evacuated all homes and businesses within a half mile of the incident site.