A historic chapel is in "danger of collapse" following a devastating fire in the early hours of Saturday.
Fire crews were called to Capel Aberfan, which was built in 1876, in Aberfan, near Merthyr Tydfil, at 2.37am.
Police evacuated four nearby homes during the height of the fire. The road remains closed to traffic.
The chapel was used as a temporary mortuary following the Aberfan disaster in 1966, in which 166 people died.
Victims - including 116 children - were killed when a coal waste tip slid down a mountain, onto a primary school and houses.
Jennie Griffiths, head of control at South Wales Fire and Rescue Service, said: "A two-storey church is in danger of collapse following a fire on Aberfan Road, Aberfan, at 2.37am.
"The police evacuated four properties during the height of the fire, crews currently remain at the scene.
"Crews from Merthyr, Treharris, Abercynon, Aberbargoed, Pontypridd and Barry attended."
A spokesman for South Wales Police said the cause of the fire was under investigation.
"South Wales Police officers are working with the fire service to investigate the cause of a fire which was reported shortly before 2.30am this morning at a chapel on Aberfan Road, Aberfan in Merthyr Tydfil," he said.
"The fire has been extinguished. A number of neighbouring properties have been evacuated as a precaution.
