Emergency crews and law enforcement were responding to a major fire at an ethanol fuel facility in Cornelius, Ore., Tuesday.

The Cornelius Fire Department posted a photo of the fire, located on North 4th Avenue, and thick black smoke to Twitter. In addition, the department issued a separate tweet of a map of the surrounding area. 

According to the agency, anyone within the red area marked on the map should evacuate, while those outside of it should shelter in place, closing all windows and doors. 

FOX 12 reported about 50 homes have been evacuated as well as a nearby Walmart. Those evacuated are urged to go to Forest Grove High School for assistance. 

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In a tweet at 5:39 p.m., firefighters said the incident was a three-alarm fire, and that crews were formulating a plan to attack the flames as safely as possible.

"This will be a long duration event and expect delays on local roadways," the department added. 

According to the news station, investigators said one of the ethanol fuel storage tanks exploded at Summit Natural Energy. First responders had to withdraw due to subsequent explosions. 

A Cornelius Fire Department spokesperson told the news outlet that because crews were unable to attack the fire, it spread to nearby buildings. Crews were reportedly letting it burn, while waiting for a foam truck to arrive from Portland International Airport. 

Natural gas to 4th Avenue has been turned off to assist with safe operations and a temporary flight restriction has been put in place for 1 nautical mile around the incident and up to 5,000 feet. Individuals who own drones are urged not to use them.

Hillsboro Police noted Southwest TV Highway is closed going into Cornelius, citing "an active fire involving fuel tanks." Police said the highway will remain closed until the situation can be made safe. As of 5 p.m., there was no estimated time for when the roadway will be reopened. 

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The Tualatin Valley Fire and Rescue said that the Cornelius Fire Department is being assisted by the Oregon State Fire Marshall hazmat team. 

Also assisting is the Washington County Sheriff's Office, who are urging people to avoid the area. North Adair between North 10th Avenue and North Yew Street is also closed.

There have been no immediate reports of injuries or missing people, but a search of the area is planned once the fire is brought under control. Metro West Ambulance is on stanby with 4 ambulances and command personnel to provide medical care as needed.

The cause of the initial explosion will be investigated when it is safe to do so.

This is a developing story. Check back for updates.