"The worth of the stolen icon is difficult to estimate in cash terms," said the Rev. Veikko Purmonen of the Helsinki Orthodox Congregation, adding that the icon is old and very valuable, the Helsingin Sanomat reported Friday.

However, Purmonen said that the icon was definitely not the most valuable treasure in the cathedral.

The icon’s origin is unknown but it originates from the 19th century and was taken to Helsinki during the World War II.

Purmonen also told the Helsingin Sanomat he believed that the thief may try to smuggle the stolen icon out of the country.

Police are investigating the incident as an aggravated theft.