The group chief executive of G4S, Nick Buckles, remains in his post on Friday after two directors quit in the wake of a review into the company's Olympic Games contract.
G4S's chief operating officer David Taylor-Smith and global events specialist Ian Horseman Sewell have quit.
More top news
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.