HARTFORD, Conn. (AP) — Connecticut environmental officials were monitoring reports Friday of sooty matter being found on parked cars throughout the state.

The state Department of Energy and Environmental Protection said it was unclear what exactly was falling from the sky or why, but it had not led to unhealthy air quality.

In a statement, the department said monitors “have not been able to determine any singular source, such as a forest fire, power plant, or transportation-related emissions, that would cause this.”

Officials said there had been reports of moderate amounts of fine particles in the air from air-quality monitors in the Northeast from Washington, D.C., through New Jersey, western New York, Connecticut and Massachusetts.

In neighboring New York, state environmental officials are investigating reports of an unusual odor in the Hudson Valley. The source of the odor was unclear.

Connecticut’s environmental agency said a cold front and rain Friday afternoon were expected to reduce those levels back into the “good” range.

The department said that air flow at 1,500 feet was following the Interstate 95 corridor northeast into New England.