PITTSBURG COUNTY, Oklahoma - The U.S. Chemical Safety Board is in the early stages of a full investigation of last week's fatal gas well explosion near Quinton. 

Five men were killed in the January 22, 2018, explosion in Pittsburg County. 

Those killed in the explosion were: Matthew Smith, 29, of McAlester, Parker Waldridge, 60, of Crescent, Roger Cunningham, 55, of Seminole, Cody Risk, 26, of Wellington, Colorado, and Josh Ray, 35, of Fort Worth. 

The CSB said last week that it deployed two investigators to the site upon learning of the incident "to gather additional facts  to assist the Board in making a decision regarding the scope of the investigation."

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CSB said investigators arrived on site on the morning of January 24 and met with the leaseholder for the well and the drilling operator.  

As of January 31, CSB said it had gathered several facts in its investigation. 

CSB said another well had recently been drilled by Patterson-UTI on the pad without incident, and drilling of the well began on January 11, 2018, and CSB was unaware of any deviations from the original well plan. 

"At the time of the incident, the rig crew had recently pulled the drillpipe and associated drilling tools out of the well in preparation to change out the drill bit," according to the CSB.

The CSB said both the well operator, Red Mountain Operator, and Patterson-UTI, the drilling company, are both cooperating with the investigation and have provided the well plan, daily drilling reports and electronic rig data.

The CSB said it plans to begin interviewing eyewitnesses and others present at the well site beginning as early as next week. 

The CSB is an independent non-regulatory federal agency that said its mission is to "drive chemical safety change through independent investigations to protect people and the environment. The agency’s board members are appointed by the President and confirmed by the Senate."