EFFINGHAM COUNTY, Ill. (WTWO/WAWV) — The National Transportation Safety Board provided an update on its safety investigation following the deadly ammonia spill in Teutopolis.

Sunday afternoon, NTSB Member Tom Chapman spoke to media in a press conference, detailing where the investigation stands and what the timeline for findings will likely be for the NTSB.

Chapman noted that the NTSB safety investigation is running parallel to Illinois State Police’s investigation into the semi wreck and chemical spill.

Chapman outlined the initial timeline for the wreck, saying a second vehicle may have been involved in performing a passing maneuver that the semi driver then reacted to, leading to the semi leaving the roadway and overturning.

Full NTSB Sunday press conference:

The tank containing 7,000 gallons anhydrous ammonia, a chemical known primarily in industrial and agricultural uses, lost 4,000 gallons of that ammonia after a hole six inches in diameter was created from the wreck.

Chapman gave a timeline for the NTSB’s investigation, saying that the investigation team will be on scene for four-six days and a preliminary findings report will be released in approximately 30 days. Chapman shared it takes 12-24 months for final findings to be released.