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Fire breaks out after explosion at Okla. oil refinery

An investigation is underway into the cause of a massive blaze at a oil refinery in Tulsa, Oklahoma. NBCNews.com's Dara Brown reports.

Updated at 6:09 a.m. ET: A blaze broke out early Thursday after an explosion at an Oklahoma oil refinery, authorities told NBC News.

A Tulsa Police Department spokesperson confirmed to NBC News that it was notified about the fire at the HollyFrontier refinery in west Tulsa at 2:21 a.m. local time (3:21 a.m. ET). 

The refinery has its own fire department, which was battling the blaze, and local authorities were on standby in case they were needed, the spokesperson said. The fire appeared under control and was being allowed to burn out, according to NBC station KJRH-Tulsa.

The explosion and subsequent blaze caused one smokestack to collapse, according to a report on local radio station KRMG. The cause of the explosion was not immediately clear.

The local and corporate offices of the Dallas-based HollyFrontier Corp. could not immediately be reached. An employee who answered the telephone at the Tulsa refinery declined to comment.

The flames reached several stories into the air immediately following the explosion but had since died down, according to a KJRH reporter on the scene. The glow from the fire could be seen from several miles away, KJRH reported.

No injuries have been reported.

KRMG reported reported that local residents stood outside their homes and watched the flames rise into the air.

A witness named only as Cody told KRMG that he and his mother were "freaking out" over the blaze.

'Not ideal' weather conditions
Weather conditions for fighting the blaze were "not ideal," according to AccuWeather, which reported temperatures of about 94 degrees with wind gusts up to 21 miles per hour.

HollyFrontier says its Tulsa refinery has a crude oil capacity of 125,000 barrels a day.

HollyFrontier describes itself as "an independent petroleum refiner and marketer that produces high value light products such as gasoline, diesel fuel, jet fuel and other specialty products."

HollyFrontier says it markets its products principally in the Southwest, Pacific Northwest and Plains states.

The company was established by a merger of Holly Corp. and Frontier Oil in 2011. Holly Corp. was ranked number 431 in Fortune magazine's 2010 list of the largest U.S. companies.

At the time of their merger, the Holly and Frontier companies totaled 440,000 barrels a day of refining capacity in their five refineries, according to The Wall Street Journal. That represented a relatively small portion of the total American refining capacity, which stood at about 17.6 million barrels a day, according to the newspaper.

NBC station KJRH contributed to this report.


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