The Grangemouth petrochemical plant, currently in the process of starting up after strike action, was believed to be the source of the dust and received a number of complaints from residents on Sunday.

However, it now appears the dust – a mixture of sand, road dust and plant matter – may have come from another, non-industrial, location.

The Scottish Environmental Protection Agency (SEPA) was continuing to analyse dust samples as The Falkirk Herald went to press. They stated it was unlikely Ineos was the source, but refused to rule out the possibility.

An Ineos spokesman said: "We received some calls on Sunday about the dust and immediately contacted SEPA to help us investigate it.
Investigations

''This is a case of industry and regulators working together to discover the identity and source of these dust deposits."

SEPA carried out their investigations on Monday after collecting dust samples the day before.

A SEPA spokesman said: "The investigation suggests the dust is a mixture of sand, road dust and plant matter. No evidence of any products of combustion was found in the dust examined.

"The analysis to date suggests the refinery is unlikely to have been the source of the dust. Measurements from monitoring locations across Central Scotland during the night of Saturday, May 3, suggest some natural process may have been in operation – resulting in elevated dust levels across a wide area.

"This is consistent with reports of dust deposition from locations as far away as Dunblane and Linlithgow."

SEPA, acting as environmental regulator for Ineos, are continuing to monitor the restart procedures at Ineos – ensuring environmental impacts are minimised by taking into account levels of air and noise pollution.