A civil rights group is demanding answers after a nun was detained by immigration authorities on her way to church in McAllen.

The League of United Latin American Citizens, known as LULAC, started a petition to find out why Leticia “Letty” Ugboaja, a 56-year-old nun from Nigeria, was detained by U.S. Immigration and Customs Enforcement officials on Sunday and released later that same day.

The group says Sister Letty is a highly regarded and well-known member of the community and should have never been detained.

Catholic bishop seeks information on “wildly disturbing” ICE arrest of nun walking to McAllen church

LULAC CEO Juan Proaño said the agencies involved must be held accountable.

"At the end of the day, these agencies can't continue to act unlawfully. Clearly something is wrong here, because if they can detain Sister Letty on her way to church, they can literally stop and detain anyone," Proaño said.

Sister Letty was taking a short walk to Our Lady of Sorrows for Mass when she was detained. Immigration authorities have yet to say why she was taken into custody. She was released after Congress members intervened. 

LULAC is also calling for oversight of immigration agencies to prevent this from happening again, and said thousands have signed the petition and plan to present it to elected officials.