(REUTERS) - A fire broke out on Monday at a Plymouth, Washington, natural gas storage facility operated by Williams Partners, and was followed by an explosion, a local fire department official told Reuters.

The fire started at the facility early on Monday and was followed by an explosion in one storage tank, said Ed Dunbar, a captain with the Benton County Fire District office.

Messages left for Williams' officials were not immediately returned.

Residents within a 3.2 km radius of the area were told to evacuate, Dunbar said.

The fire's cause was still unknown. Local media have reported some injuries.

According to its website, Williams operates a liquefied natural gas (LNG) storage facility in Plymouth. To create LNG, natural gas is cooled to minus 260 degrees Fahrenheit at which point it condenses into a clear, orderless liquid, according to Williams' website.

The LNG is stored in large tanks, built with a double-wall design, Williams said.