Homes and businesses were evacuated in Chorley town centre after a suspected gas leak.
A police cordon closed off Market Street to traffic, from the town hall to the Big Lamp roundabout, after a 999 call at 9.20am.
More than 20 police officers and a fire crew responded to the incident, and closed the street for more than five hours to allow tests to be carried out by the National Grid and United Utilities.
A gas leak was later ruled out after it was found that the strong smell had been caused by heating oil that had accidentally been leaked from a business into the sewer.
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