The source of a mysterious smell coming off the waterfront and wafting through Bellingham remained a mystery Thursday afternoon, Sept. 19, as reports continued to come in to official agencies.

More than 100 callers reported a sulfur, natural gas, methane or petroleum smell in Bellingham Wednesday evening, Sept. 18.

Callers to 911 first reported the smell in the area of Fieldston Road, south of Fairhaven, around 5 p.m. About 20 calls continued to come in as the smell apparently moved north toward the Columbia and Birchwood Neighborhoods, said David Doll, deputy chief of Bellingham Police. The calls dropped off around Alderwood Avenue.

Cascade Natural Gas heard from about 80 callers who thought there might be a natural gas leak, said spokesman Mark Hanson. Technicians from Cascade checked the area from about 5 to 10 p.m. but determined it was not a natural gas issue, Hanson said.

Bellingham firefighters checked each reported area with gas detection equipment, and though they could smell the odor in the air, the equipment did not detect any dangerous levels, low or high, of oxygen or other gases, Assistant Fire Chief Bill Hewitt said.

A second wave of calls came in Thursday afternoon, reporting a similar strange smell.

Though several people suspected the smell might be coming from a train going through the area, that was likely not the culprit, Hewitt said.

"After Marine Drive the tracks head inland through Ferndale, and we had no calls going up that direction," Hewitt said. "And there were no reports where the tracks start in Skagit County. You would expect it would have started there or continued if it was something on the train."

A BNSF Railway Co. spokesman said the company hadn't received any complaints about the smell.

The Northwest Clean Air Agency and the Department of Ecology did not know what might be causing the smell.

Bellingham Public Works is currently making improvements at Post Point Wastewater Treatment Plant, but that shouldn't be causing a sulfur or natural gas smell, said Freeman Anthony, city project engineer.

"The smell coming from the plant is more of a stinky, poopy smell," Anthony said. "We've had a few calls about that, but I don't think it'd be carrying throughout the city."

This is the second wave of reports of a natural gas smell along the waterfront this summer. Callers flooded 911 dispatchers in mid-August, prompting Bellingham Fire Department to issue a statement that firefighters believed the smell was coming from decaying plant matter at low tides. There were no trains traveling through the area during the August reports.

Bellingham had an 8-foot high tide at 5 p.m. Wednesday. It is unknown if the two events are related.