HARRIS COUNTY (CBSDFW.COM/AP) – Authorities say a drop in water pressure caused a fire at a petrochemical plant near Houston to intensify overnight and spread to additional storage tanks.

The Deer Park Office of Emergency Management says the fire spread early Tuesday to two additional tanks, bringing to eight the total number of tanks overwhelmed by flames at Intercontinental Terminals Company in Deer Park, about 15 miles southeast of Houston.

Two of the tanks were empty but the others contain components of gasoline and materials used in nail polish remover, glues and paint thinner.

Initially officials had said, because of the fuel feeding it, the fire was likely to burn for another two days. The water pressure later normalized and authorities sticking to that timeline.

The fire erupted Sunday and firefighters have been working ever since trying to control the blaze. Despite the roaring flames, the company says the risk of explosion is “minimal.”

ITC has said all employees have been accounted for and no injuries have been reported. A huge plume of smoke could be seen for miles, including from the Galveston Ferry, about 35 miles southeast of the blaze. Officials estimated the plume rose 3,000 feet to 4,000 feet into the air.

Monday afternoon, ITC spokeswoman Alice Richardson said fire crews had made progress battling the blaze as three of the tanks were now only intermittently on fire.

A report done by the Center for Toxicology and Environmental Health, a local environmental consultant hired by ITC, shows the air quality around the facility was below levels that would represent a health concern, Richardson said. Data for the company’s report was collected from multiple locations in Deer Park and in surrounding communities from Sunday through Monday morning.

Harris County Judge Lina Hidalgo said Monday the county is performing its own monitoring of air quality and reviewing data from the state.

“The latest information available doesn’t show levels beyond a threshold that would make this dangerous,” she said.

Hidalgo, the highest elected official in the county, said if conditions change, residents would be alerted about any potential health hazards.

A shelter-in-place order was issued Sunday for Deer Park, which has about 34,000 residents.

The order was lifted early Monday after air-quality tests showed no unsafe levels of chemicals, according to the city.

But city and county officials warned that smoke from the fire could cause skin and eye irritation, and respiratory issues. Schools in the area were closed Monday as a precaution. Deer Park and the school district in neighboring La Porte planned to resume classes on Tuesday.

Isaias Lopez’s grandson stayed home after classes in La Porte were canceled. The two walked his dog at a park on Monday and looked at the dark plume of smoke coming from the fire.

“I’ve seen the smoke since yesterday,” Lopez said. “It’s been blowing like that. Today it’s been making more wind than yesterday. So it’s not so bad as long as the smoke don’t come around this area. I guess we’ll be OK.”

Fire crews used foam to protect storage tanks that have not caught on fire

“We are controlling the fire and keeping it off the rest of the tanks,” said Ray Russell with Channel Industries Mutual Aid, an organization that coordinates rescue and emergency capabilities of the local petrochemical industry.

Russell estimated the fire would burn for another two days. He said firefighters were now in a defensive mode.

Harris County Fire Marshal Laurie Christensen said investigators from her office are on the scene of the fire and are still working to determine the cause of the blaze.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)