OSHA also confirmed its agency is now involved in the incident.
Fire officials say the spill happened around 3:30 p.m. on Wednesday at Martin Asphalt in the City of South Houston near Collage Avenue and Galveston Road.
On Thursday, crews were dressed in hard hats, hazmat suits, and neon vests as they worked to clean up the 50,000 gallons of tar that spilled from a tank. The cleanup, South Houston officials said, will take days.
According to a Friday update from the Texas Commission on Environmental Quality, the tank failed during filling operations. The agency added that the material that spilled off-site onto the soil ditches was contained and "the asphalt emulsion appears to have hardened and does not pose a threat to migrate further."
"Typically, what they will do is anything that gets into the soil, that soil will be removed and taken to a facility to be remediated and incorporated into something else. We used to send it to actually be turned into asphalt," Christine Brandford, a geology professor at Lone Star College-Tomball, said.
With rain in the forecast, nearby neighbors said they worry it could cause dangerous runoff. Bradford said that after 24 hours, the material is much safer to come into contact with rain.
"If there is a cap on it that solidified, there won't be nearly as much risk as if it were still hot and still fluid," Bradford said.
City of South Houston officials said air quality is safe. But as the day warmed up on Thursday, neighbors say the fumes intensified. One nearby resident who goes by "Layllow" said he's felt nauseated and ill, and worried it would make his son sick.
"My main concern is that I have a little kid and I don't want him to have any side effect or sickness or whatever else would happen from breathing in all this smell because I can tell you, you can smell it really bad out here right now," Layllow said.
ABC13 has also been looking into Martin Asphalt, the company where the spill occurred.
The City of South Houston said they have no records of documented concerns.
Outside the current OSHA investigation tied to this incident, ABC13 found no other records of OSHA involvement.
About a year ago, one odor complaint was made to the Texas Commission on Environmental Quality.
Eyewitness News reached out to TCEQ on whether any action was taken on that complaint. TCEQ said the complaint was referred to Harris County in April 2025 and advised contacting the county for more information.