Authorities from Allegheny and Butler counties say residents had nothing to fear from a mysterious yellowish-green cloud that appeared yesterday morning near Bakerstown in Richland.

There was no confirmation of a chemical release, which had been suspected earlier yesterday after authorities received numerous 911 calls about the cloud. Officials from the state Department of Environmental Protection, Butler County Emergency Services, an Allegheny County hazardous materials team and local police and firefighters were dispatched in northern Allegheny and southern Butler counties shortly before noon yesterday and detected no chemical releases.

Local residents complained of a chlorine or sweet smell in the air, but there were no evacuations, ill effects or hospitalizations, officials said. Local police asked citizens to remain indoors while it was being investigated, but apparently the cloud dissipated quickly. By the time some emergency response teams arrived, it was gone with the wind.

Allegheny County health officials said tests revealed air quality was normal and they received no reports of chemical accidents at local industries or escaped chlorine at swimming pools.

The National Weather Service suspects the cloud may have been the result of an inversion.