By Robert Pigott
BBC Religious Affairs Correspondent
Sister Kathy Stein, right, helps run a shelter for the homeless
When the Vatican began an inquiry seven months ago into the "soundness" of American nuns, it adopted a discreet approach.
But as details have emerged about the investigation into the beliefs held by nuns - and of the way they worship - the disquiet and irritation felt in religious communities has started to spill into the public arena.
A working paper delivered recently by the Vatican to the leaders of American nuns was interpreted by many as a sign that the hierarchy in Rome is worried about a liberal drift among them.
The sisters are increasingly anxious about what that might mean.
Nuns once worked mainly in Roman Catholic schools and hospitals, but since the sweeping reforms of the Second Vatican Council in the late 1960s they have decided for themselves how best to do good in the world.
Sister Kathy Stein, of the Sisters of St Joseph of Carondelet, is executive director of Thomas House, a shelter for homeless families in Garden Grove in Orange County, California.
Thomas House, with its 16 apartments in a secure compound, its language and parenting classes, its food bank and its activities for children, is a secular organisation with no formal link to the Church.
Sister Kathy has never worn a habit, and moved out of the convent long ago to live among the people she serves.
But she says the Church need have no worry about the way she meets her religious calling.
"I would see it as a reason for hope that our message of love and respect and concern for people is expanding beyond the walls of a Catholic institution... that we are able to bring God's word to people by who we are and how we minister to them," she said.
Manuela Aguilar and her daughter, Terri, say they would have been living in their car had there not been space for them at Thomas House.
She is glad the shelter is not linked with the Church, and would not want to see Sister Kathy wearing a habit, or living in a distant convent.
"Sister Kathy does splendidly well as she is, acting as a Good Samaritan out in the community running this organisation and not being stuck in a convent," she said.
But senior figures in the Vatican are concerned that as nuns respond to the changing needs of US society, some have become too liberal.
Recent guidance about the investigation - known as the "apostolic visitation" - reveals questions about whether nuns take part in daily mass, and "the soundness of doctrine held and taught" by them.
Traditionalists have long been concerned that some sisters might be flouting Church teaching on sensitive issues such as homosexuality and the ordination of women as priests.
The investigation will also ask for a description of "the process for responding to sisters who dissent publicly or privately from the authoritative teaching of the Church".
The process has been welcomed by some more conservative orders.
Helen Hull Hitchcock, of Women for Faith and Family, said the inquiry into the claim by some nuns to "complete self-determination" independently of the Church hierarchy, was decades overdue.
But Francine Cardman, an academic at the School of Theology and Ministry at Boston College, claimed that the investigation was an attempt to establish an official interpretation of the teaching of the Second Vatican Council.
She warned that nuns had in the past frequently been restricted as to what kind of work they could do, or even "returned to the confines of the cloister".
Sister Mary Mackay says the Vatican shouldn't impose its views
Sister Kathy's Mother Superior, Sister Mary Mackay, oversees 360 nuns, all but 90 of them living and working in a wide range of jobs in the community.
Sister Mary says the Vatican hierarchy inhabits a very different world, and could not expect to impose its own idea of religious life on the culture inhabited by American nuns.
"The culture encourages everyone to be very tolerant and open-minded," she said.
"To imagine that a dictum sent by somebody we don't know who lives very far away would take hold in this culture, to imagine that, is really a stretch."
The Church says it doesn't want to impose its own model of life on nuns but to revitalise religious orders.
Officials say the Vatican has a genuine concern for the "quality of life" of the approximately 60,000 sisters.
But many nuns believe the investigation is intended to rein them in, while others warn that a male hierarchy wants to regain control of them as women and as a free workforce.
There could be consequences for those who disappoint the Vatican.
Annette Ciketic helps run Beacon House in San Pedro, California, a hostel for men recovering from drink and drug addiction.
Annette belongs to the Immaculate Heart, a community of former nuns who had to leave the Church 40 years ago because they refused to toe the Vatican line.
She claims that the Church's idea of proper work for nuns would rule this work out.
Trini Luna likes the brand of spirituality at Beacon House
"That would have been unheard of in the early days for a group of nuns to be working in a home for alcoholic men, it wasn't acceptable," she said.
"We would be teaching their children and witnessing (the effects of) their abuse in the classroom... but God forbid we should ever deal with the adults and especially the fathers."
Trini Luna says the prayers and sermons he heard by going to church did little to help him overcome his addiction to drugs.
He says he has encountered a more flexible spirituality at Beacon House, which has had far more effect.
"Living by these spiritual principles my life has changed tremendously," he said.
"It doesn't have to be in a Church way. It can be in a recovery home in the centre of Los Angeles."
The Sisters of St Joseph insist that they too are satisfied with the way they are doing their duty.
Sister Kathy Stein says she does not need to preach to those who use the shelter for them to receive the Christian message.
"They know me as Sister Kathy. They know I'm a Catholic sister. I'm ready to talk about the gospel if they want to. That's enough."