Firefighters have declared the chemical fire at Port Metro Vancouver extinguished, meaning investigators will be able to start working to determine how it started.

A shipping container loaded with an industrial disinfectant and bleaching agent went up in flames Wednesday afternoon, sending a huge plume of smoke into the air over East Vancouver.

Crews battled the blaze for more than 24 hours before Vancouver Fire and Rescue Services announced it was out shortly before 5 p.m. Thursday.

“The scene is safe and secure,” the department said in a statement.

The cause of the fire remains a mystery, but firefighters expect to open the container after nightfall if wind conditions allow.

Authorities confirmed the chemical inside is trichloroisocyanuric acid, a compound often used in swimming pools, exposure to which can be similar to breathing in bleach.

Police and city staff used bullhorns and social media to alert the public about the smoke, but a total of 15 people showed up at hospitals in Vancouver, Burnaby and North Vancouver with irritated eyes and lungs.

None were admitted; all were assessed and released.

Vancouver Coastal Health medical health officer Dr. Meena Dawar said there were very few adverse health effects from the smoke “given the size of the plume and amount of exposure.”

Dawar said the provincial drug and poison information centre fielded 60 calls from people with concerns about exposure to the chemical.

Environmental response

The fire also raised concerns about environmental contamination. A berm was set up at the port, where salvage and environmental contractors have been brought in to help clean up.

It’s unclear how much of the chemical may have reached the water, but Dr. Peter Ross with the Vancouver Aquarium’s Ocean Pollution Research Program said he’s cautiously optimistic any marine impacts will be minimal.

“The nature of this product is such that it’s going to break down,” Ross said. “The receiving environment is fairly large so I’d expect dilution.”

The port’s vice-president of planning and development, Peter Xotta, confirmed Thursday that trichloroisocyanuric acid passes through the port regularly.

Last year, 500 containers of the chemical were transported at the port, Xotta said, and there are three or four more containers at the scene currently.

“I can’t speak to whether they’re all part of the same shipment,” he said. “We know this particular container was in transit from China to Eastern Canada via one of the Canadian railways.”

There is no evidence that the container that caught fire was mislabeled or its contents counterfeit, Xotta said.

City praises response

One of the reasons health officials cited for the blaze’s minimal health effects was the efficiency with which the fire department, the health authority, the city, and the police coordinated the effort to keep people indoors during the height of the smoke.

“We knew really quickly what chemical we were dealing with, and that was really important,” Dawar said. “We were able to get the messages out reminding people to stay away from the plume.”

McKearney began his remarks by thanking Vancouver’s citizens for complying with an order to stay inside and close their windows during the height of the blaze on Wednesday.

He also thanked the city’s first responders, the operators of the port, regional transit companies, and local hospitals for their responses.

“Yesterday was an event that the city hasn’t experienced in quite some time,” Wood said. “I just want to take this opportunity to say how proud I am of how everybody worked together. We’ve learned a lot. We’re still going through what we could do better next time, but for the most part I think things went really well.”

City manager Penny Ballem said the city feels the same way. While she’s heard a few anecdotes about things that didn’t go well -- including some people whose vehicles were towed while they were following the shelter-in-place order -- there’s a lot to feel good about and a lot to learn from the experience, she said.

“It was a good solid response,” Ballem said. “This is the closest we’ve come to a major evacuation across part of our city in many, many years.”

With files from CTV Vancouver’s Lisa Rossington and Maria Weisgarber and The Canadian Press