Pasadena residents are complaining about what they call a gas odor, but investigators are having a hard time finding the source.

According to the Pasadena Department of Emergency Management (PDEM), “The Pasadena, Texas, Fire Department has responded to multiple locations to investigate these reports and, at this time, has not detected any readings indicating unsafe air conditions.”

They’re working on a possibility that the smell may be connected to the burning of excess natural gas, called “flaring,” at a N. South Street company called Next Wave Energy Partners, but so far any connection is not proven.

Work is underway by the Harris County Pollution Control district to take atmospheric samples to evaluate air quality of nearby neighborhoods, the PDEM said on Tuesday.