Two men have been arrested in connection with the investigation into the death of university graduate Catherine Wells-Burr, police said.
A 31-year-old man and a 38-year-old man remain in police custody where they are being questioned.
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Mladic, now 75, was the military commander of Bosnian Serb forces in the 1990s, who fought against the Bosnian Croat and Bosniak armies.
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His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."