An Irving Paper employee was treated in hospital after butane gas was detected at the mill on Wednesday, the company has confirmed.

The employee went to the Saint John Regional Hospital at around 9:30 p.m., reporting "headache symptoms" following her shift, J.D. Irving Ltd. spokeswoman Mary Keith said in an emailed statement to CBC News.

"The employee underwent tests prescribed by medical professionals and was subsequently released," said Keith, without elaborating in the late night email.

Butane is a colourless, highly flammable gas that can cause nausea, asphyxia and arrhythmia if inhaled.

"The evacuation of the mill and [air quality] testing was underway prior to the employee reporting to hospital," said Keith.

The company is maintaining contact with the employee and co-operating fully with WorksafeNB, she added.

Irving Paper, Irving Wallboard plant and J.D. Irving Ltd. offices on Bayside Drive all remained closed Thursday night, but employees could be back to work on Friday, based on preliminary air quality tests at the mill, said Keith.

"Employees will return to these work sites when two separate tests have determined we meet the safe, regulated exposure levels," she said.

"Employee safety is our top priority and a responsibility that we take very seriously."

About 300 people work at the mill, located at 435 Bayside Dr.

Butane is not used there, but emergency crews continue to deal with a butane leak discovered down the street Monday at Irving Oil's Saint John East Terminal, located at 350 Bayside Dr.

About 30 area homes have been evacuated and Bayside Drive remains closed to all traffic from the Courtenay Bay Causeway to Red Head Road.

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J.D. Irving Ltd. has brought in extra air quality monitoring experts and equipment to expedite the process, said spokesperson Mary Keith. (CBC)

"Extensive" testing is expected to be completed overnight at the mill, wallboard plant and Bayside offices, said Keith.

J.D. Irving Ltd. has brought in experts who specialize in air quality monitoring and testing as well as additional testing materials to assist the Saint John fire department and Irving Oil and expedite the process, she said.

As of 6 p.m. Thursday — about halfway through the first round of air quality tests at the mill — no butane has been detected, said Keith.

"Continued positive test results will mean call backs and duty assignments for employees of the Irving Paper and Irving Wallboard will begin mid-morning tomorrow."

Bayside offices are also expected to reopen in the morning, she said. Employees will be updated at 7 a.m.

'No imminent risk of ignition'

Irving Paper mill on Bayside Drive in Saint John

Mill workers noticed odours and alarms starting around 8:30 p.m. on Wednesday. (Google Street View)

Irving Paper workers were first alerted to odours and alarms around 8:30 p.m. Wednesday, prompting the evacuation and shut down of mill operations, and the neighbouring Irving Wallboard plant, said Keith.

Although air quality tests Wednesday "confirmed no imminent risk of ignition," test results from certain areas within the mill "exceeded the regulatory standards," she said without elaborating.

People in day shift operations, technical and maintenance employees were asked to stay home until the situation was resolved.

About 65 nearby residents are spending a fourth night at a hotel and motorists on the city's east side will face another morning navigating around the road closure on Bayside Drive Friday.

Platoon Chief Brian Wilson, the incident commander at the site overnight Wednesday, had seemed hopeful some residents might be able to return home on Thursday morning.

"A lot of the work has been completed and this morning they will have a meeting and make an assessment of getting people back into their homes," he had said.

"The area immediately around the spill, there's still some stuff on the ground that's got to be dealt with, so there will be three or four houses that will be the last ones to have their people moved back into them, but that's what the plan is for the morning, is to do an assessment of the homes in the area with safety being the primary concern."

Butane leak, Irving Oil Saint John East Terminal, Bayside Drive

Bayside Drive remains closed to traffic between the Courtney Bay Causeway and Red Head Road, as the cleanup of a butane gas leak continues. (CBC)

Wilson said the air quality levels vary in different areas of the evacuation zone, which includes 30 homes on River Avenue, First Street East and Second Street East and at 66-72 Spruce St.

"We'll do some gas testing of each and every one of them and make sure they're clear, and that's where we'll go from there," he said.

The readings should be zero when people return to their homes, said Wilson.

He thought they might be able to reduce the size of the evacuation zone, nothing there hadn't been butane detected in the First and Second Street areas for some time.

"In other areas, where we moved the product out of the way, that's where you'll get your readings," he said.

Mild temperatures aiding cleanup

Wilson expected the rain and mild temperatures forecasted for Thursday and Friday would help with the remediation work.

"The cold weather allowed us to do things one way, and with the warmer temperatures, any product that may be left is going to evaporate," he said.

"It'll disperse it that way. Mother Nature will look after things."

Buildings that have been tested and deemed safe for re-entry are:

  • Industrial Security at 430 Bayside Dr.
  • CFM at 380 Bayside Dr.
  • 2 First St. E., the old East Saint John School.