ROUGH CUT (NO REPORTER NARRATION) A fire at a Houston-area petrochemical storage site continued to rage Tuesday and was expected to burn for two more days, officials said on Monday, sending thick black smoke into the air for miles around.

Firefighters were making progress seeking to contain the blaze at Intercontinental Terminals Co (ITC), with the number of giant storage tanks on fire reduced to six from seven earlier, said ITC spokeswoman Alice Richardson.

The blaze at a site along the Houston Ship Channel in Deer Park, Texas, began Sunday (March 17) when a leak from a tank containing volatile naphtha ignited and spread to others in the same complex, the company said.

The tanks hold tens of thousands of barrels of products used to boost gasoline octane, make solvents and plastics.

The blaze has not disrupted nearby refineries or shipping at the country's busiest petrochemical port, authorities said.

The Houston Ship Channel is home to nine U.S. oil refineries that process 2.3 million barrels per day (bpd), or 12 percent of the national total.

Authorities said on Monday that the air quality around the facility was testing within normal guidelines.