Flames ripped through an historic Victorian church causing thousands of pounds worth of damage.
Firefighters were called to the Greek Orthodox Church in Carlton Hill, Brighton, at about 2.45pm today.
They are currently still at the scene assessing the damage to the grade II listed building.
Members of the church, who watched the drama unfold, said they were in a state of shock.
Zacharias Koullas, treasurer of the church, said: “I left the building about an hour before and everything was fine. Then I got a call telling me it was on fire.
“I just don’t know what has happened.
“We have no idea of the damage caused as we have not been allowed into the building.
“All we can do is hope that it’s not badly damaged, and anything that is we will do our best to restore.”
Police closed surrounding roads and set up traffic diversions.
It is believed up to 50 children have been evacuated from a nearby summer fair.
Fire investigation teams will attend the scene this evening to establish the cause of the fire.
Incident commander Tony Gurr said six fire engines attended the blaze.
He said: “Large volumes of smoke were coming from the building.
“We were told on arrival that nobody was trapped.
“The fire started in the ground floor and spread to the first floor and some of the roof space towards the rear of the building, but there is no evidence of structural damage.”
The 1,200 capacity building was built in 1840 as a free church for Brighton’s poor.
The former St John the Evangelist Church closed in 1980 and was taken over by the city’s Greek Orthodox community in 1985.