What's that smell in New Castle County, Delaware and in Delaware County, Pennsylvania?

Early Thursday morning, emergency response agencies in the area said they were aware of the odor and were looking into it. Turns out the smell was coming from the refinery in Trainer, Pennsylvania.

"It smelled like a sulfur smell," Joe Montoro said.

"It smells like gasoline, yeah, gasoline," Adeola Babatunde said.

The Woodlyn Volunteer Fire Company said Monroe Energy was conducting a "burn-off" that is producing a plume of smoke and flames. The Elsmere Fire Company shared that there was an equipment failure at the refinery.

"This morning, I woke up and smelled it and I was like that's strange I hope there's nothing leaking in our house," Crystal Goldman said.

Monroe Energy later confirmed that a power outage at the Trainer refinery, which is less than a mile away from the Marcus Hook refinery, caused the strong odor. 

According to Monroe Energy, at around 6:30 a.m., they began their safety shutdown procedures. The shutdown process sends gases to the flare stack, which acts as a safety relief valve to reduce pressure. The process resulted in visible flaring for about two hours.

At about 9:30 a.m., Monroe Energy said they started receiving reports of odors about 10 miles south of their facility in New Castle County, Delaware. 

There were over 40 readings in multiple locations, spanning from Marcus Hook down to the City of Wilmington.

Monroe Energy said its Refinery Air Monitoring Team's test found that there is no risk to human health.

"The refinery is in stable condition, and there has been no flaring for several hours," Monroe Energy said in a statement. "We sincerely apologize for any concern and inconvenience this unpleasant odor may have caused residents."

David Rockett, who works nearby, shared images showing a flame and plume of smoke emanating from the refinery.

The New Castle County Emergency Management and Citizen Corps said they were aware of reports of an outdoor odor and were working with Monroe Energy. The agency advised residents with respiratory issues to remain indoors for the moment out of an abundance of caution.

And the Talleyville, Delaware Fire Company said there is a gasoline-like smell throughout the area, having received more than 30 911 calls about the smell starting around 8:30 a.m. Thursday.

"Between 8 and 10 a.m., we fielded approximately 34 calls," Talleyville Fire Chief Michael DiMauro said.

DiMauro said his department responded to each call to help investigate a possible cause. Talleyville also advised homeowners and businesses to turn off their air conditioning as a precaution.

"We had a lot of businesses where their units were running, rooftop units sucking in air, and that's what was spreading the odor through the building," DiMauro said.