VANCOUVER -- A mysterious and unpleasant stench started wafting through Port Moody over the weekend, and officials are still trying to determine where it came from.

Port Moody Fire Rescue said the strange smells first arrived on Saturday evening, prompting "numerous" calls to their department and 911.

Despite reaching out to FortisBC, Metro Vancouver and the B.C. government, firefighters said there were no answers by Monday morning – though the smell still lingered in parts of the city.

"PMFR continues to be as puzzled as our citizens when it comes to the noxious odours," the fire department tweeted.

Port Moody Fire Rescue has not responded to a request for more information from CTV News, including how people have described the stench. On social media, one man said it smelled "like rotten eggs."

Metro Vancouver regional officials said 15 complaints have come in since Sunday morning, with some describing the odour as "gas, chemical or sulphur-like."

"Metro Vancouver officers have conducted odour surveys in the area and are following up with potential sources in the vicinity," Ray Robb, division manager of environmental regulation and enforcement, said in an email. "The source of the odour remains unknown."

FortisBC said it dispatched a service technician to Port Moody over the weekend to investigate the smells, but determined natural gas was not the cause.

"Safety is our main priority and all reports of gas odour are always investigated," said Diana Sorace with the utility's communications team. "There were no readings of natural gas in the area."

Officials said anyone who notices the smells in the coming days should contact Metro Vancouver's air quality complaint line at 604-436-6777.

Port Moody Fire Rescue said if people believe something is posing an immediate threat to public safety, they should call 911 instead.