Assistant Chief Fire Officer Simon Moore said Mr Cox was not on a call at the time.
He added: "The circumstances of his death have not been established. We are saddened and upset by this tragic news and our thoughts are with his family and colleagues at this very difficult time."
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The 23-year-old, who won best song at the Mobo awards last year, was sentenced to eight months.
The tenants were forced into 'sleeping shifts' as night workers would swap with those who had daytime hours at the Wembley property.
The incident comes just days after four fans were suspended for abusing Manchester City's Raheem Sterling.