Pro-Russian rebels have said the death toll during two days of fighting in the eastern Ukraine city of Donetsk has now risen to 50.
The prime minister of the rebels' self-styled Donetsk People's Republic (DNR) Alexander Borodai told Russia's RIA news agency: "We have lost more than 50 volunteers."
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Transport Secretary Chris Grayling believes Network Rail should share the responsibility with private train operating companies.
Two vehicles were swallowed up by the sinkhole on Sunday night, killing Dora Linda Nishihara and injuring one man.
Elliott Livingstone, aged three, spent most of his life in hospital before the operation in April.