A mysterious burning odor in Delaware County has resurfaced, prompting some 911 calls, writes Chris O’Connell for Fox 29 Philadelphia.

The odor, which some describe as wood or plastic burning, seems to resurface every few months.

This time, Delaware County Emergency Services received numerous calls in just one day. The smell started late Monday night. So far, there’s no official word on what it might be.

“We received calls all day starting at 7 a.m.” said Delaware County Emergency Services Director Tim Boyce.

“Actually I thought a house was on fire,” said one man.

Social media lit up with complaints, from Eddystone, Broomall, Rose Valley, Villanova, even New Jersey.

Some thought it smelled like bug spray. Others thought it was a return of the Canadian wildfires. 

The South Media Fire Company responded to a Rose Valley house call for a report of an “odor of burnt plastic in the area.”

Delaware County officials initially speculated that the odor was from industrial stacks near Chester or Marcus Hook but couldn’t explain why reports were coming from as far away as New Jersey.

The whole thing seemed to disappear by Tuesday evening.

Read more about an ongoing burning odor in Delaware County at Fox 29.