Gardai are trawling through CCTV camera footage in a bid to identify those behind the theft of the preserved heart of Dublin's patron saint, St Laurence O'Toole, from Christchurch Cathedral.
Senior officers admitted last night that the motive for the theft on Saturday morning remained a mystery.
Initially gardai were examining the possibility that the thief, or thieves, might have stayed in the cathedral overnight on Friday and then prised open the iron bars protecting the wooden heart-shaped box holding the heart.
But the latest theory is that the heart was still present when the cathedral opened on Saturday morning at 9.30am.
The theft was spotted at around 12.30pm on Saturday. Gardai pointed out that valuble chalices and candlesticks were ignored and nothing else seemed to be missing.
The Dean of Christchurch, the Reverend Dermot Dunne, said the heart had no economic value but was a priceless treasure that linked "our present foundation with its founding father, St Laurence O'Toole".
He said the relic was bolted to the wall in a metal cage and it would have taken a lot of effort to extract it from there.
Gardai have asked anyone who visited the cathedral between Friday evening and lunchtime on Saturday and spotted any unusual activity to contact Kevin Street garda station on 01 6669400 or to call the garda confidential line 1800 666111.