Churchgoers had to be evacuated from the Holy Family Church in Londonderry last night after an adjoining outbuilding was engulfed in flames.
CCTV from the scene revealed a group of young people entering the back of the premises just before the fire started.
PSNI Detective Constable Fielding said: “At this stage we believe two males may have been involved in starting this fire and we are keen to identify them.
“We would like to hear from anyone who was in the area at around the time of the fire or anyone who may have information regarding this crime.”
NIFRS Group Commander Andy Burns was said: “The fire was very intense and spread onto the roof of the chapel. The crews battled temperatures well in excess of 150 degrees celcius.”
Speaking to journalist Leona O’Neill last night, Holy Family’s Fr Paddy O’Kane said it “was a big shock”.
“What can I say? Why are they doing this? Words fail me…just to say how disappointed I am that anybody would do that to the church”, he said.
SDLP councillor Shauna Cusack described it as a “reckless act”.
She said: “I don’t know what they were trying to achieve – it put people at risk.
“It also put the fire service at risk too. I really can’t understand the mindset of people who would want to destroy a place of worship and somebody’s home.”