Philadelphia business owners and residents are asking Pennsylvania Commonwealth Court to immediately suspend the city’s indoor mask mandate, days after some of them sued the city over the return of the restriction.

The group, represented by attorney Thomas King III, on Wednesday filed a motion seeking an emergency injunction to halt the mandate, which the city began enforcing Monday.

The filing, which asks the court to schedule a hearing to quickly decide the matter, says the individual persons and businesses represented in the lawsuit face “irreparable harm” from the masking order, which they call illegal.

It notes that the federal masking mandate for airlines and public transportation was just struck down by a federal judge. The Justice Department filed a notice of appeal in that case Wednesday.

The federal judge’s ruling “is consistent with the argument we are making,” King said in a phone interview.

Mayor Jim Kenney’s office did not immediately respond to a request for comment.

Philadelphia is the only large American city to have brought back a mask requirement amid rising COVID-19 case counts. The city on Monday reported that cases had increased more than 50% in the last 10 days and hospitalizations had doubled in the last week.

» READ MORE: Why is Philly requiring masks again when other cities aren’t? We asked the experts.

“I suspect that this wave will be smaller than the one we saw in January,” Philadelphia Health Commissioner Cheryl Bettigole said last week. “But if we wait to find out and to put our masks back on, we’ll have lost our chance to stop the wave.”

The return of the city’s mandate began on the same day a federal judge in Florida struck down the federal mask mandate on trains, planes, buses, and other public transit. The ruling has caused mass confusion across the Philadelphia region, where masks are now no longer required on SEPTA, New Jersey Transit, and PATCO, as well as in Ubers, Lyfts, or on flights serviced by certain airlines. However, indoor venues must require them, unless they instead require proof of vaccination.

Ongoing litigation over both the federal transit mask mandate and Philadelphia’s local rules could now potentially add to residents’ sense of whiplash over face coverings.

» READ MORE: The Justice Department will appeal the order voiding the mask mandate for travelers

It remained unclear Wednesday evening whether the Biden administration would ask for an emergency stay to immediately reimpose the mask mandate on public transit.

The CDC said in a statement Wednesday that “masking in the indoor transportation corridor remains necessary for the public health.”

Across Pennsylvania, average daily case counts and hospitalizations are still as low as they’ve been since the summer, but Philadelphia health officials say the trends in the city are a reason to be cautious.

In reporting this week that hospitalizations had also increased, the city health department said in a statement: “This is a worrisome sign that this wave could be more dangerous than we had hoped.”

King, the attorney for the group of Philadelphians trying to overturn the mandate, takes issue with the city’s metrics for reimplementing restrictions, and told The Inquirer on Monday, “We simply say the entire scheme is not legally correct.” King was among the lawyers who successfully moved to strike down the statewide school mask mandate.

» READ MORE: Philly’s latest mask mandate is relieving COVID anxiety for some. For others, it’s making things worse.

The city is using a tiered system to determine when restrictions should be implemented or relaxed. The system takes into account case counts, hospitalizations, and the percentage increase in cases. The city has said it would reinstate various restrictions when different thresholds in two of those three categories are met.

If cases and hospitalizations continue to rise, the benchmark could be met for the city to again order restaurants and bars to require patrons to show proof of vaccination. The city has declined to comment on whether the vaccine mandate could return.

Philadelphia dropped its mask mandate in early March, around the time that other cities across the country were doing the same.

As the mandate returns in Philadelphia, other cities have not indicated they will follow suit, with New Jersey Gov. Phil Murphy saying last week he’d be “shocked” if the Garden State did so.

The Associated Press contributed to this article.