SEPTA is now providing free face masks for riders, but the transit agency warns that supplies are limited and only those who really need a mask should take one.

The surgical masks will be placed in plastic bags aboard various buses, trains and trolleys starting Wednesday, SEPTA spokesman John Golden said. Signs will point people to the masks, and they’ll be able to grab their own without a driver having to hand it to them.

The masks will be available on trains on the Market-Frankford and Broad Street lines, as well as vehicles departing 69th, 15th, Suburban and Jefferson stations, Golden said. He added that supplies are limited and that SEPTA currently has no plans to order more once they run out.

“We’re asking people to only take one, if they even need it,” Golden said.

SEPTA has taken steps in recent weeks to try and contain the spread of COVID-19 by encouraging riders to wear face coverings and by reducing the number of passengers aboard public transit vehicles.

The new face mask program comes only days after Philadelphia police forcefully pulled a man, who was not wearing a mask, off a bus after he refused a bus driver’s request to get off. However, Golden insisted that the incident, which was captured on camera and garnered national attention, was not what triggered the new face mask program.

“It’s promoted by the fact that we’re promoting the safety of our operators and our riders based on CDC guidelines,” he said.

Though people are not required to wear a face covering while riding SEPTA, Golden said the agency is “strongly urging” them to do so.