The MBTA told its users last Friday that its policy that almost all passengers wear face coverings while riding public transit will be enforced going forward, with fines being levied on anyone on trains, buses, and ferries who does not follow Gov. Baker’s updated executive order.

This is a reversal from the agency’s position earlier this year that a previous mask order could not be firmly enforced.

Under Baker’s new approach, all residents over the age of 5 are required to wear a mask or cloth face-covering over both their mouth and nose when in public, including on public transit. Individuals with relevant medical conditions are exempt, but all others are required to comply.

Transit Police are now authorized to enforce the order on MBTA vehicles and in stations, empowered to issue civil fines up to $300 per violation, T officials said.

The agency told employees to inform any commuters not wearing masks of the updated order. If riders do not comply at that point, employees will inform the T’s Operations Control Center, “who will report and coordinate next steps with Transit Police,” the MBTA said.