A Philadelphia person who was tested for the new coronavirus does not, in fact, have the infection, according to state laboratory results announced Wednesday. But another potential case is under investigation.

Health officials have been directed to err on the side of caution in deciding whom to test, now that cases with no known source of infection suggest the virus is spreading from person to person in California, Oregon, Washington, and beyond. The U.S. Centers for Disease Control and Prevention now advises testing anyone with respiratory symptoms and a history of travel to an affected country — not just China, the original source — or anyone with severe respiratory illness that has no other explanation.

However, testing capacity remains limited. Pennsylvania’s public health lab in Exton, where the suspected case sample was processed, can do only 25 tests per day, officials have said. The Exton lab is using a polymerase chain reaction (PCR) kit issued by the CDC, which has been criticized for being unprepared for rapid, widespread testing.

Pennsylvania’s turnaround time for testing also may be lengthy, based on how long it took to release results of the suspected case. The negative result was announced Wednesday at 5:30 p.m., 20 hours after the city Department of Public Health alerted the media that a possible case was being investigated.

That is hours longer than the turnaround time described on Tuesday by state Health Secretary Rachel Levine.

City health department spokesperson James Garrow did not provide additional details about the new possible case.

A handful of possible cases have been identified in the city since January, and so far all the patients have turned out to be sick with some other illness.

As of Wednesday, 128 patients with coronavirus infections had been identified in more than a dozen states, including New York. Symptoms in most patients have been mild. So far, no patients have been identified in Pennsylvania, though on Wednesday evening, New Jersey officials announced a “presumptive positive” case in Bergen County.