Health authorities are warning that people could feel the effects of the chemical fire at Port Metro Vancouver up to 24 hours after being exposed.

A massive chemical fire Wednesday forced the closure of the port and hundreds of people were ordered to stay in and close their windows while heavy smoke drifted over parts of downtown Vancouver.

As of Thursday morning, the fire continued to smoulder, but officials said the smoke was no longer a health concern.

Health authorities are warning that people could feel the effects of the chemical fire at Port Metro Vancouver up to 24 hours after being exposed. (CBC News)

Patricia Daly, chief medical officer of Vancouver Coastal Health, said it appears nobody was seriously injured by the toxic fumes.

"If it is a high enough concentration it could cause damage to the airways, but we don't believe anyone was close enough based on the information we had," said Daly.

"We've had no one come to hospital by ambulance experiencing that type of damage."

But she said people, especially those with pre-existing lung problems, could experience wheezing or difficulty breathing and if so, should seek medical attention.

"People with asthma or other lung diseases do need to monitor themselves over the next 24 hours if they have been exposed to the smoke," she said on Wednesday.

She said health-care facilities across the city are prepared to help with those concerns.

"You may feel burning and stinging in your eyes, you might feel it in your throat or when you breathe," Daly said.