PHILADELPHIA — The parkway where Pope Francis will celebrate Mass will be able to hold about 250,000 people and overflow crowds that organizers expect will bring the turnout total to a million or more will be able to view the service on jumbo TV screens, officials said in an update Friday.

The Secret Service told The Associated Press about 80,000 people with tickets distributed mostly through local parishes and an online lottery will fill the first three blocks in front of the pope’s altar for the Mass on Sept. 27.

The rest of the mile-long Benjamin Franklin Parkway, stretching to City Hall and also within a secured perimeter, is projected to hold from 150,000 to 200,000, Special Agent David Beach said.

Organizers expect more than 1 million people for the Mass and as many as 750,000 for a concert and festival featuring the pope the night before, also on the parkway. The pope will parade along the event grounds both days.

Secret Service Director Joseph Clancy said the Philadelphia leg of Francis’ tour presented “enormous challenges” because, unlike in New York and Washington, D.C., all of his public events will be outdoors.