A man died and a woman was seriously injured when the roof of a house collapsed.
The couple were in a bedroom at their home in Knight's Fold, Bradford, when debris fell on them in the early hours of the morning.
The man, 47, died while the woman, 28, was taken to hospital. Her injuries are not thought to be life threatening.
Neighbours reported hearing a "loud bang" and a woman screaming shortly after 04:30 BST.
A family from a neighbouring property, including three children, were taken out of their house unhurt.
Paul Wright, 30, of nearby Southfield Lane, said: "At about half past four this morning I heard a big, loud bang, like an explosion.
"I came out with my partner to see what had gone on and noticed one of the neighbour's roofs had collapsed."
Speaking of the injured woman, Mr Wright said: "It took them the best part of an hour, over an hour, to get her out the house.
"They had to take the full window out to carry her out."
Iqbal Zahir, who also lives on Southfield Lane, which joins on to Knight's Fold, also reported hearing a loud bang at about 04:30.
"It's really sad. It was the chimney, they need repairing, these are old houses," he said.
Awais Asghar, who works in a nearby corner shop, said: "A chimney collapsed straight on to their roof and straight through and unfortunately the man passed away. He was a regular customer of mine. They were a nice couple."
Det Insp Claudine Binns said work was under way to make the building safe and police had launched an investigation with Bradford council to determine the cause of the collapse.
She said the family in the adjoining house would be rehomed with the authorities "working to support everyone involved in any way we can".
Emergency services were called just after 05:00 BST to reports of a "structural collapse".
Road closures are now in place in the area while police officers, firefighters and structural engineers carry out work.
Officers from West Yorkshire Police are preparing a file for the coroner.