It was the smell that could not be identified.
Pittsburgh firefighters, Allegheny County Health Department officials and mobile units from Equitable Gas spent much of Friday morning trying to figure out what caused a natural gas odor in three city neighborhoods.
Equitable Gas spokesman Scott Waitlevertch said the calls began about 9:30 a.m. Friday from residents in the Strip District who smelled a strong natural gas odor in the air. Quickly after that, calls began coming from Lawrenceville then Shadyside, he said. By about 1 p.m. calls about the smells stopped.
The smell would dissipate from an area after a while and then move on to a new area, moving west to east across the city, which was strange, health department spokesman Guillermo Cole said, because the wind Friday morning was moving east to west.
But no matter who tested it or where or when, in every case, mobile air sampling detectors indicated it was not natural gas, Mr. Waitlevertch and Mr. Cole said.
"There is a gas odor out there similar to natural gas," Mr. Waitlevertch said Friday morning. "But we've cleared all of the areas. There is no issue, no leaks, we've discovered from any of our lines.
"We just can't tell what it is," he said.
The Pittsburgh Bureau of Fire apparently doesn't know what it is, either. Though firefighters responded to calls about the smell as well, Chief Darryl Jones said he had no information to release about the incident.
Mr. Cole said in an email response to questions that officials "did some real-time indoor and outdoor air monitoring for hydrocarbons, which includes natural gas" and only found normal levels.
But health officials smelled the same odor that residents were experiencing, he said.
"There was a natural gas type odor in the air at the time and it dissipated by 10 a.m." in Lawrenceville, he said.
The department "also collected an indoor air sample where there was an odor of natural gas that is being analyzed in the lab, which may or may not indicate the presence of something. The lab results, however, will not be known until Monday at the earliest," he wrote.
Though some people complained that the smell upset their stomachs, he said, "it doesn't appear that there was exposure to anything harmful."
Several employees of Children's Hospital of Pittsburgh of UPMC in Lawrenceville were bothered by the smell that hit the hospital a little after 9 a.m., said Eric Hess, vice president at the hospital.
"It was strong enough that it caused some people to want to go outside, particularly if they were on one side of the building" on the west side of the hospital, he said.
For a time, Children's officials held in the front lobby a growing group of patients and their families who were coming for appointments until test results -- from the city, county, gas company and Children's own safety officials -- all showed there was nothing to worry about.
"It was maybe 30 minutes between smelling it and being concerned, and putting everyone at ease and going back to their appointments," he said.
Similar incidents of a traveling gas smell occur from time to time, Mr. Waitlevertch said, and they sometimes are found to be a truck or a train traveling through an area carrying something with an unusual odor emanating from its load. Other times it's found to be traveling sewer gas, he said.
But none of those circumstances appears to be the case in Pittsburgh Friday, he said, and gas, fire and health department officials continued to investigate.
The gas company had received 15 calls as of 1 p.m., he said, "and rightfully so; customers should call us when they believe they smell natural gas."
Sean D. Hamill: firstname.lastname@example.org or 412-263-2579.