The New Brunswick Energy and Utilities Board is investigating the butane leak at Irving Oil's Saint John East Terminal under the provincial Pipeline Act.
The EUB wants to determine the cause of the leak at 350 Bayside Dr., whether procedures were followed, and "what, if any procedures need to be implemented to prevent it from happening again," said senior adviser David Young.
The leak, discovered Monday morning, forced the evacuation of some businesses in the area and about 65 residents.
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Butane is a colourless, highly flammable gas that can cause nausea, asphyxia and arrhythmia if inhaled.
Bayside Drive also remains closed to traffic between the Courtenay Bay Causeway and Red Head Road as emergency crews continue to clean up the site and repair the four-inch-diameter line that runs to the Irving Oil refinery.
'This is a process that could take months to finish.' - David Young, EUB
The EUB is an independent quasi-judicial board charged with regulating public utilities. It licenses pipelines for hazardous materials and automatically investigates any leaks.
Irving Oil filed a preliminary incident report to the board on Wednesday, as required under the act, said Young.
But he said he could not disclose any details, citing the ongoing investigation.
He did say the EUB has asked for some additional "specific information" and expects a more comprehensive report at a later date. There is no set deadline, he said.
"This is a process that could take months to finish," said Young. "The board likely won't be releasing any information until the investigation is complete."
The Department of Environment will also be investigating to determine if any charges should be laid and what remedial action may be required.