Neighbors asked why hazardous materials teams were on Circle Drive Monday and Tuesday.
Framingham Fire tests indicated a reading of "volatile organic compound," said Framingham Assistant Fire Chief John Magri. "But we couldn't identify the type or source."
Thus Framingham Fire called in a state hazardous materials team.
When that agency couldn't identify the type of compound and cause, it called in the Massachusetts Department of Environmental Protection (DEP) Monday around 7 p.m.
A DEP Field Assessment Support Team (FAST) and vehicle was in the neighborhood investigating Monday night and all day Tuesday.
DEP spokesman Joe Ferson said air samples were taken inside all three homes. He said volatile organic compounds (VOC) were identified in the sump pump areas of two of the homes.
The FAST team was also testing and investigating near and along the Sudbury River.
Tuesday afternoon, Ferson said the VOC was likely a low-level fuel source, such as home heating oil, diesel gasoline, etc and not a solvent.
He said the fuel could have seeped into the basement area after it was accidentally spilled on a paved surface, through a storm drain or into soil. The DEP is still investigating where the low-level fuel came from.
Ferson said the homeowners are safe to live in their properties, as there is no "immediate hazard."
He said the DEP would be back in the neighborhood to conduct a clean-up post the snowstorm. He said the DEP field team needs dry-weather conditions.
Selectman Giombetti said Monday night one of his Circle Drive neighbors detected a strange odor, at times, over the weekend and reported it to Framingham Fire on Monday.
Giombetti said he first learned of the hazmat situation, when a firefighter came knocking on his door to come inside and test the air quality on Monday.
The odor originated at 21 Circle Dr., but was also detected at both 3 and 7 Circle Dr.