(Children play behind a curtain to separate the men and women in a prayer hall at the Islamic Cultural Center of New York in the Manhattan borough of New York August 26, 2010. REUTERS/Lucas Jackson)

American Muslims grew in number over the past decade, outnumbering Jews for the first time in most of the Midwest and part of the South, while most mainline churches lost adherents, according to a census of American religions released.

The number of Muslim adherents rose to 2.6 million in 2010 from 1 million in 2000, fueled by immigration and conversions, said Dale Jones, a researcher who worked on the study by the Association of Statisticians of American Religious Bodies.

“Christians are the largest group in every state, but some of the things we found interesting was the growth of the Mormons, who reported the largest numerical gain in 26 states,” said Jones, who presented the report on Tuesday to a conference in Chicago.

The number of Mormons, whose Utah-based church’s formal name is The Church of Jesus Christ of Latter-day Saints, grew by 45 percent to 6.1 million in 2010, according to the census, which asked 236 religions to count their own adherents. Family members of adherents were generally included in the numbers.