Christians make up about 83 percent of unauthorized immigrants to the United States, a report issued by the Pew Forum on Religion and Public Life has found.
These undocumented believers mainly come from Latin America.
The percentage of Christians among the 11.1 million unauthorized immigrants is greater than that of the native population.
Some 80 percent of Americans claim to be Christian.
"Many of the remaining 17 percent are religiously unaffiliated, and fewer than one-in-ten unauthorized immigrants are estimated to belong to non-Christian groups," said Pew.
The report focused mainly on legal immigrants to the U.S.
They make up three quarters of the nation's 43 million foreign-born residents.
Pew noted that "the religious makeup of the legal permanent residents is quite different from that of unauthorized immigrants."
Their report indicated that while Christians still make up the majority of legal permanent residents, their numbers are falling. The 2012 figures show that they make up 61 percent of legal permanent residents, a drop from 68 percent in 1992.
In 2012, over one million immigrants were granted permanent resident status and 620,000 of them were Christians.
The U.S. government does not keep track of the religious affiliation of its immigrants.
Therefore, the Pew findings are estimates.
They are based on government statistics concerning place of origin and survey data reflecting the religious self-identification of immigrants.
Over the same period the percentage of religious minorities among legal permanent residents rose from 19 percent to 25 percent. The number of Muslims and Hindus who are legal permanent residents doubled.
These figures reflect a demographic shift which has taken placed in the U.S. over the last 20 years. Legal immigration from Europe has decreased during that time, while it has increased from Asia, African and the Middle East.
Unauthorized immigration is a major issue in the Unites States.
The U.S. Congress is seeking to pass bipartisan legislation to reform the nation's laws to give them a pathway to citizenship.
Pew noted in a previous report that most Americans favor finding a way to allow unauthorized immigrants to remain in the United States.
Of the 70 percent who want unauthorized immigrants to stay, only 44 percent want them to be able to apply for citizenship.
Christians have launched a campaign to allow amnesty for unauthorized immigrants, which is a shift from a previous hard-line stance among conservative Christians.
Last month, the Wall Street Journal noted how evangelical pastors are supporting a pathway to citizenship for unauthorized immigrants based on biblical teachings which strangers should be welcomed.