Officials are asking Skippack residents to allow their homes to be tested for the chemical odor before they can return.
Problems arose Sunday evening after a resident reported a strong odor. Subsequent testing of that home and several others led officials to identify basement sump pumps as the source.
But the composition of the noxious smell isn't clear. Fire Chief Haydn Marriott says samples have been sent to several labs for analysis. He says results are expected later Monday.
Officials have scheduled a news conference for 11:45 a.m.
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