"We have done the extensive lab analysis, and there is nothing conclusive as to a particular chemical signature from the samples we took," said Charles Sturcken, a spokesman for the city’s Department of Environmental Protection.
Pressed for details on what the city was doing next, Sturcken said that unless the bad smell returned, it was finished with the matter.
"The investigation of the odors from last Monday has been concluded," he wrote in an e-mail.
To date, investigators in both states say they have no idea what the gas was or where it came from and are largely out of leads to check.
"Odors are elusive," Makatura said.
IPBiz notes that extensive lab analysis could not detect a mercaptan, or other sulfur compound, is a bit scary. IPBiz previously noted that many news organizations immediately related the smell to [odorless] natural gas, not contemplating the reality that natural gas by itself doesn't smell (a sulfur compound is added) or the possibility that the perceived compound might have originated other than from natural gas.