The detective leading the hunt for missing chef Claudia Lawrence will make a nationwide television appeal for information.
Miss Lawrence, 35, was last seen 11 days ago near her home on Heworth Road, in York, and police fear she has come to harm after meeting up with someone she knows.
Detective Superintendent Ray Galloway, of North Yorkshire Police, will make an appeal on BBC1's Crimewatch programme.
Prayers have been said for Miss Lawrence's safe return at churches across her home city of York.
Around 350 people gathered at York Minster, where Miss Lawrence's father, Peter, is a volunteer steward, to pray for the chef and her family - Mr Lawrence, her mother Joan and her older sister Ali.
Leading the prayers during the Holy Communion service, The Reverend Canon Glyn Webster, chancellor of the Minster, said: "We pray for the safety and well-being of Claudia Lawrence. As we pray for her, so we pray for her family, for Peter, for Joan, for Ali, her family and many friends, during this time of waiting and of great anxiety."
Prayers were also being said at Holy Trinity Church, in Heworth, York, where Miss Lawrence lives, and in Malton, Norton and Old Malton where her mother attends church.
Mr Lawrence, a solicitor from Slingsby, North Yorkshire, issued a statement earlier inviting people to join the family in praying for Miss Lawrence.
He said: "For our part, we are trying to keep strong in our faith through this difficult period, in the belief that hope will prevail and that, once again, we will be physically reunited with Claudia, and express our continued, everlasting love for her."
Miss Lawrence was last seen on March 18 after she finished work at the University of York's Goodricke College and has not been in contact with anybody since around 8.30pm that night.
