The woman who lunged at Pope Benedict and caused him to fall to the floor at the start of his Christmas Eve mass was psychologically unstable and was not armed, the Vatican said on Friday.

In its first formal statement on the episode that shocked the Catholic world on Thursday night, the Vatican identified the woman as Susanna Maiolo, 25, a dual Italian-Swiss national.

It said she was detained and taken to an undisclosed medical facility for necessary treatment.

The pope's schedule will not be changed as a result of the incident. He is due to deliver his Urbi et Orbi (to the city and the world) message and blessing at noon (1100 GMT).

The statement said Maiolo had managed to grab the pope's vestments and he lost his balance and he slipped to the floor.

Maiolo, who was wearing a red, hooded sweatshirt, jumped over a barricade and lunged at the pope at the start of his Christmas Eve mass in St Peter's Basilica late on Thursday, provoking screams from members of the congregation.

Vatican spokesman Father Federico Lombardi said she was the same person who had tried to jump a barricade to reach the pope at last year's Christmas Mass.

French Cardinal Roger Etchegaray, 87, who has been in frail health recently, fell to the floor in the confusion and was taken away in a wheelchair. He suffered a broken femur and will have to undergo surgery but is not in serious condition.

The pope, dressed in gold and white vestments, was helped up by security men and after a few seconds continued the procession up the center aisle to celebrate the Mass. He seemed calm and unfazed during the rest of the ceremony.

FIRST SERIOUS SECURITY BREACH

There have been relatively few security breaches in Benedict's pontificate, which began in 2005. In 2007 a German man jumped over a barricade in St Peter's Square as the pope's jeep was passing during a general audience and tried to board the vehicle.

The most serious attack on a pope in the Vatican was in 1981 when Turkish gunman Mehmet Ali Agca shot and nearly killed Pope John Paul II in St Peter's Square.

Thursday's incident, which left Vatican security guards visibly shaken and bishops stunned, happened at the start of a Mass at which Benedict led the world's 1.1 billion Roman Catholics into Christmas.

It raised again the issue of how vulnerable the pope can be if he wants to maintain contact with the public.

It's surprising that it happened inside St Peter's, because the security there has changed a great deal in recent years and is much more tight than it used to be, the Archbishop of Westminster, Vincent Nichols, leader of Catholics in England and Wales, told the BBC.

But there it is, I'm sure those arrangements will be reviewed and greater care will be taken, he said.

While visitors to St Peter's Basilica must pass through metal detectors and spot checks, security once they get inside is relatively light. Vatican security is shared by a police force and Swiss Guards.

For the first time in recent memory, the Christmas Eve mass started two hours before midnight in order to give the pope more time to rest before Friday's main Christmas event at noon.

In his homily to more than 10,000 people inside Christendom's largest church, the pope urged the faithful to rediscover the simplicity of the nativity message.

He recounted the traditional Christmas story of Christ's birth in a manger in Bethlehem and urged Catholics to put aside the complexities and burdens of daily life and rediscover the path to God.

We live our lives by philosophies, amid worldly affairs and life and rediscover the path to God.

We live our lives by philosophies, amid worldly affairs and occupations that totally absorb us and are a great distance from the manger, he said.

In all kinds of ways, God has to prod us and reach out to us again and again, so that we can manage to escape from the muddle of our thoughts and activities and discover the way that leads to him, he said.