Dalzell, the chair of Saint John's Citizens Coalition for Clean Air, said the refinery already emits many different types of "volatile organic compounds" into the air: organic chemicals that have a high vapour pressure and can be hazardous to human health.
"On behalf of all New Brunswickers, our thoughts are with the workers affected and with the community of Saint John", Premier Brian Gallant said in a tweet.
CBC News reports people nearby reported a "bed shaking explosion" and police are urging people to avoid the area.
"We now understand that all employees and contractors working on site have been safely accounted for", Irving Oil reported in a Twitter post.
The source said he believed the explosion was within the section of the plant that houses the hydrogen unit.
"We refine a wide range of products for our wholesale and retail markets, including gasoline, diesel, heating oil, jet fuel, propane and asphalt", the website says.
Irving Oil has confirmed that they are responding to a "major incident" at the Saint John, New Brunswick facility.
"I heard a rumbling, roaring sound", Guimond said.
He noticed black smoke coming from the refinery and when he went to get a closer look, noticed huge flames shooting 30 metres high into the sky.
Rob Beebe felt the explosion from his apartment on Martha Avenue, a few streets over from the refinery. Streets in the area have been closed as authorities monitor the situation.
Steeves said the incident reminded him of a similar event in the late 90s, when the same refinery suffered a similar explosion which left one person dead.
'We are actively assessing the situation at this time and will share more information when available'.