(CNN) - A cloud of black smoke continues to emanate from a fire at a petrochemical storage facility in suburban Houston that has burned since Sunday.
But for some near the sprawling grid of oil refineries and chemical plants, incidents like this are one of the risks of life along the Houston shipping channel.
The cause of the fire at Intercontinental Terminals Company is under investigation. Officials said it could take until Wednesday to put out the blazes in tanks filled with gas, oil and chemicals, according to ITC.
Meanwhile, after temporary closures of Highway 225 and schools and the lifting of a shelter-in-place order, Deer Park and surrounding communities are reopening.
The facility is among many along the channel, one of the country's busiest seaports and home to its largest petrochemical complex. Natural gas flames, towers of smoke and gassy smells are common in this part of Harris County, Deer Park resident Pennie Tinker told CNN affiliate KPRC.
But she'd never experienced anything like this before.
"It comes with the territory and you're going to be warned if anything happens as soon as you see something, you know, or you just watch the news or get your information," said Tinker, who has lived in Deer Park for more than 20 years, according to KPRC.
"It was kind of scary at first, you know, because I've never seen anything that dramatic," said Tinker.
Blaze could take two more days to contain
While emergency responders work to contain the blaze, officials sought to reassure the public, saying the plume of smoke did not appear to have affected air quality.
Air monitoring test results that ITC released Monday indicate that conditions are "below levels" that represent health concerns, ITC spokeswomen Alice Richardson said. All ITC employees are accounted for, and no injuries have been reported, she said.
"Consistently favorable" air quality monitoring results, along with the lifting of the shelter-in-place order and forecasts calling for the smoke plume to keep moving west, led to the decision to reopen Deer Park schools on Tuesday, the district said. And there has been no significant change at the site, Superintendent Victor E. White Jr. said in a statement.
The school district is restricting outside activities and calling for home games to be moved to other locations or different dates until the fire is over.
Restaurants in Deer Park were open when CNN contacted them Monday night. But residents described mixed feelings about the column of smoke looming above their homes.
Sandi Pentecost, who lives about a mile away from the facility, told KPRC that although she was concerned, she trusted authorities to get the situation under control.
"The kids are really scared, I mean they went and packed little suitcases and stuff in case we have to evacuate. The adults, we're calm, but yet, that inner fear of what's going to happen, we don't know," she told the station.
How it started
The fire began in a single tank on Sunday afternoon and spread to a second tank, ITC said.
By Monday morning, seven of the facility's 242 tanks were involved in the fire, and the blaze spread to an eighth tank before 5:30 a.m., the company said.
Later, however, Richardson said only six tanks were affected and that one of the tanks originally cited was empty and another was falsely reported on fire.
Authorities reopened Highway 225 early Monday and lifted an order that residents of Deer Park stay inside with with their windows closed and central cooling or heating units turned off.
Firefighters are using foam and water to douse the blaze, Richardson said. They hope that once the fire is contained, they can close the tank valves and the fire will put itself out.
One tank stores naphtha and another contains xylene, both of which ITC described as "components in gasoline."
Xylene is a solvent that occurs naturally in petroleum, ITC said. Swallowing or breathing the substance can cause death, while nonlethal exposure can cause eye, nose, throat and skin irritation, among other maladies, according to the National Library of Medicine.
Naphtha is a petroleum product resulting from the distillation of natural gas or crude oil, the library says. It can be an eye and nasal irritant.
The latest tank to catch fire contains toluene, which is used in the production of nail polish remover, glue and paint thinner, ITC said.
Toluene occurs naturally in crude oil and is used as a gasoline additive, "and damage to the central nervous system is the main concern following exposure to toluene in the air," the library says.
The other tanks hold "gas blend stocks used in the production of finished gasoline, and base oil commonly used as machine lubricants," ITC said.
According to ITC, the Deer Park terminal opened in 1972 and has capacity for 2.2 million cubic meters -- more than a half billion gallons -- of storage for "all kinds of petrochemical liquids and gases, as well as fuel oil, bunker oil and distillates." The facility has ship and barge docks, rail and truck access and pipeline connections.