About 150 people were evacuated from a Pennsylvania neighborhood after volatile organic compounds began leaking in homes.

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Something is stinky in a Montgomery County, Pennsylvania, neighborhood, and the mysterious odor has caused more than 100 people to evacuate their homes.

"When neighborhood residents reported an odor, hazmat crews were called in to check it out. The fire department says they found a high reading of hydrogen cyanide,​ but they believe another chemical was actually causing the strange smell." (Via WBFF)

"Crews are still trying to figure out what that odor is, running tests to determine the source of the smell. So far no one has gotten sick." (Via WCAU)

Although the investigation is still underway, WPVI reports authorities believe the smell could be coming from sump pumps in the basements. Volatile organic compounds, such as those leaking, can come from hundreds of different sources including gasoline, paint, paint thinners and solvents used for degreasing or dry cleaning. (Via Getty Images)

"They checked levels, and they said we have a one point something and our neighbor had a three point something. So they told us to open up all our windows, and we had to evacuate and stay outside until further notice." (Via WPVI)

According to the U.S. Geological Survey, "[Volatile organic compounds] are ground-water contaminants of concern because of very large environmental releases, human toxicity, and a tendency for some compounds to persist in and migrate with ground-water to drinking-water supply."

As for health effects related to VOCs, the Centers for Disease Control and Prevention explains it really depends on how harmful the chemical is and a person's sensitivity level. Some symptoms of exposure can include skin irritation, headaches, dizziness, nausea and more.

The Philadelphia Inquirer reports Montgomery County's hazardous-materials experts as well as eight different fire companies have responded to the incident.

"Two energy companies that operate in the area said they tested their systems on site and determined they were not the source of the odor. ... Natural gas distribution systems were operating normally. And ... Texas Eastern natural gas transmission pipeline was operating correctly."

Many of those who evacuated were sent to an emergency shelter at a nearby school, and some people were sent to the hospital as a precaution but showed no symptoms of illness.