31609
On September 11 , 1957 , a plutonium fire occurred at the Rocky Flats Plant , which resulted in the significant plutonium contamination of surrounding populated areas .
 Rocky Flats Plant
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Rocky Flats Plant