By CBS3 Staff

PHILADELPHIA (CBS) — The road to recovery has hit a bump. Cases of COVID-19 are now increasing in Pennsylvania. Just as our region moves into the green phase of reopening, Philadelphia health officials say a second wave has started in the city, and because of that, masks will now be mandatory in the city.

Big caution flags are being waved by Philadelphia Health Commissioner Dr. Thomas Farley because of the increased cases, mainly among young people. He says the city might keep restrictions in place longer than planned.

“Today, we will be issuing a mandatory mask order for the City of Philadelphia,” Farley said.

The health commissioner says masks will now be required inside all public locations in the city and outside if people aren’t six feet apart.

“There will be limited exceptions, such as an exception for children under the age of 8,” Farley said.

It’s an effort to curb what the health commissioner calls a second wave of COVID-19.

After weeks of progress and lowering numbers, there’s an uptick in cases, which is not related to the increased testing.

“We have noticed in particular, a spike in cases among teenagers between the ages of 16 to 19 that appear to be from them attending social events,” Farley said.

“We’re really concerned,” said Dr. Deborah Pierce, with the Einstein Healthcare Network.

Pierce says the emergency department at Einstein has been seeing evidence of a second wave.

“Patients that are in their 20s and even younger than that, and that’s a huge concern because that’s a population that everybody thought was somewhat protected and now we’re seeing those patients with more and more symptoms, not just asymptotic disease,” Pierce said.

Doctors say spikes in cases around the country — that now includes Pennsylvania — are mainly among younger people, with the danger being them spreading the virus to vulnerable populations.

“We’re recommending people in Philadelphia not travel to high-instance areas and request that people traveling from high-instance areas to Philadelphia self-quarantine for 14 days,” Farley said.

Even with a green reopening designation from the state for all of southeastern Pennsylvania, Philadelphia kept many restrictions in place for another week.

The plan to lift them on July 3 is now in jeopardy.

“Given the numbers we have right now, we are not meeting our target for reopening next Friday,” Farley said.

While Philadelphia has seen an increase in COVID-19 case counts, the city is in far better shape than the rest of the country as a whole. Cases counts are up more than 50% nationally.

And locally, officials say they are no longer seeing a spread within prisons and nursing homes.

Farley is especially concerned about allowing indoor activities to resume next Friday, like dining in restaurants. The virus spreads more easily inside.

He said wearing a mask is a requirement but it won’t be enforced by police.

CBS3’s Stephanie Stahl and Alexandria Hoff contributed to this report.