A rights group filed an emergency lawsuit in federal court Friday against top officials of U.S. immigration and homeland security departments, alleging they have unconstitutionally denied lawyers' access to immigrants in a prison in Oregon.

Immigration and Customs Enforcement transferred 123 immigrants in early June to the federal prison in Sheridan, Oregon, because other holding facilities have been overloaded since the Trump administration enacted a "zero tolerance" policy in April involving people entering the U.S. illegally.

The American Civil Liberties Union of Oregon filed the lawsuit in Portland on behalf of the detainees, who are mostly from Mexico and Central America. The lawyers say they've been denied meaningful access to the detainees, many of whom escaped violence in their home countries and are seeking asylum in the U.S.

"The U.S. Constitution protects everyone who is on U.S. soil," said Mat Dos Santos, legal director of the ACLU of Oregon. "You have fundamental rights to due process of law. You can't just throw them in prison."

An interfaith group, meanwhile, announced it would be holding Sunday morning services outside the prison. The Interfaith Movement for Immigrant Justice, which is organizing the services, is based in Portland.

"With Attorney General Jeffrey Sessions invoking Romans 13 to validate the immoral separation of immigrant children from their families, this can no longer be a time for 'business as usual' for Christian communities," said the Rev. Michael Ellick of First Congregational United Church of Christ in Portland.

Last week, Sessions cited a Bible verse urging obedience to the laws of government "for the purpose of order."

Among the people being held in the medium-security prison is Luis Javier Sanchez Gonzalez, whose family was separated at the border when they sought asylum at a port of entry, the ACLU said.