Created: 07/23/2014 4:53 PM KSTP.com
An emergency manager says this week's fire at a Williston oil field supply company likely burned dozens of different chemicals that were stored there.
Williams County Emergency Manager Mike Hallesy says the fire at Red River Supply will need to be fully extinguished before investigators can determine what caused it.
He also said the half-mile voluntary evacuation zone that was cordoned off has been lifted since the fire is mostly out.
North Dakota Department of Health Air Quality Division director Terry O'Clair says air quality tests at the site showed levels "that would not raise concern."
Hallesy says the air quality in Williston was worse when smoke from Canadian wildfires passed over western North Dakota several weeks ago.
The fire began about midnight Monday and burned most of Tuesday.
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