At least 20,000 people fled in panic when a 40-foot-tall kerosene tank caught fire at an oil tank farm in this northern city, threatening adjacent tanks. It was 10 hours before residents could return home.

No serious injuries were reported in Tuesday's blaze at the storage facility operated by the government oil monopoly Pem-ex in a residential area.Authorities said some firefighters suffered minor burns in the eight hours it took for them to bring the inferno under control.

About 900,000 gallons of kerosene were in the steel tank when it ignited in an explosion at about 10:10 a.m. MDT.

The government news agency Notimex said area residents had been protesting the tank farm's presence and the tanks were to have been relocated months ago, but new facilities have not been completed.

The conflagration threatened 14 other tanks on the farm that were filled with millions of gallons of gasoline. Fire and smoke spiraled more than 150 feet above the plant.

Fearing the worst, authorities evacuated people living around the plant.

One estimate said as many as 200,000 people fled their homes.

"There were all kinds of accidents in the road. The whole city was running (away from the site)," said Luis Alonso Hernandez, 26, who works at the plant. "You could see the flames and black smoke from miles away."

Chihuahua, 230 miles south of El Paso, Texas, has 550,000 residents and is the capital of Chihuahua, the largest in area of Mexico's 31 states.

The cause of the fire was under investigation, but company officials said maintenance work was going on at the time of the explosion.