As the Pope and bishops continue to call for the just and humane treatment of migrants, a new survey has found that the population of unauthorized immigrants in the U.S. may be rising.

In a Sept. 24 preliminary estimate, the Pew Research Center concluded that a decline in the U.S. population of unauthorized immigrants following the 2007-2009 recession has stalled.

Studying U.S. Census data, the research organization noted that between 2007 and 2009, the population of undocumented immigrants in the country fell from 12.2 million to 11.3 million people.

However, as the economy has recovered, the sharp decrease in undocumented immigration in the country has slowed, and Pew estimated that as of March 2012, the number had climbed to 11.7 million, according to government data.

In a Sept. 6 op-ed in the New York Daily News, Cardinal Timothy M. Dolan of New York said that "no one can be proud of the enormous underclass of undocumented workers that's been allowed to form" in the United States.

Cardinal Dolan, who is the president of the U.S. Conference of Catholic Bishops, pointed to "millions of our neighbors who live on the margins, have their families fractured and are easily exploited." 

Pope Francis has also commented on the pressing issue of immigration. On Sept. 24, he called for the faithful to help "enable others to see, that migrants and refugees do not only represent a problem to be solved, but are brothers and sisters to be welcomed, respected and loved."

The preliminary estimate from Pew noted that nearly two-thirds of unauthorized immigrants live in six states: California, Florida, Illinois, New Jersey, New York and Texas, and that a majority of the unauthorized immigrants are from Mexico.

The news coincides with the U.S. bishops' campaign for immigration reform in the United States, which has included Masses, educational opportunities, and public forums.

National lawmakers have debated possible reform measures while the bishops have concentrated their focus on earned legalization programs for undocumented workers currently in the country, worker programs to allow foreign-born workers to enter the country safely and legally, the preservation of families, due process rights alongside enforcement, and efforts to address the root causes that drive migration.

"We want to try to pull out all the stops," said Kevin Appleby, the director of migration policy for the U.S. Bishops to the New York Times of the campaign.

"They have to hear the message that we want this done, and if you're not successful during the summer, you're not going to win by the end of the year," he said on the initiative's urgency.