By Tim Jimenez, John McDevitt

PHILADELPHIA (CBS) — The World Meeting of Families is underway at the Pennsylvania Convention Center in Center City Philadelphia. Tuesday marked the first day of the conference that has brought thousands of people from all over the globe into the city.

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The participants started to sign in at 6 a.m. for an event organizers say is bigger than ever.

At the last World Meeting in 2012 in Milan, Italy, 7,000 people took part. This year, that number has jumped to 18,000.

It takes a lot to run the event and many of the volunteers aren’t just local.

“I’m happy to be a part of this. I’m loving Philadelphia. I’m loving the pope,” said Mark, who came from Michigan to take part. “I’m from the Archdiocese of Detroit. Back in April, I got an email from the Knights of Columbus that said the Archdiocese of Philadelphia was looking for volunteers for the World Meeting of Families and the Papal Visit, and so I signed up.”

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He will be at 21st and Winter Streets for this weekend’s events on the Ben Franklin Parkway. He’ll be busy for sure, but he says thrilled to be in the pope’s presence.

As KYW’s John McDevitt reports, a ribbon cutting ceremony was held to officially open the World Meeting of Families conference.

A children’s choir from various parishes sang. Some attendees in the audience waved flags of their countries during the ceremony.

Mayor of Philadelphia Michael Nutter delivered remarks.

“The city of Philadephia is deeply honored and excited to host the World Meeting of Families Philadelphia 2015.  A conference that brings together people from all over the world in celebration of the family the sanctuary of love and life,” said Mayor Nutter.

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The Mayor was joined by several others including Archbishop Charles Chaput and representatives of the World Meeting of Families to cut a red ribbon to officially open the World Meeting of Families conference.