Anti-Semitic death threats have been sent to Chelsea boss Avram Grant in a package containing a mysterious powder, police said today.

The club's training ground at Cobham, Surrey, was sealed off after a member of staff opened the package yesterday. A note addressed to Grant claimed the powder was lethal.

A police source confirmed that the note to Grant, 52, included the words: 'You are a back-stabbing Jewish b******. When you open this letter you will die a very slow and painful death.'

Death threats of a sexual nature were also made to Grant's wife, Tzofit, a well-known television personality in the couple's native Israel.

A spokesman for Surrey Police said: 'We were called to Chelsea's training ground at Cobham at 12.15pm yesterday after they received a suspicious package.

'A white powder contained within the package was analysed by specialists from Surrey Fire Service and was determined to be a harmless substance.

'Detectives are continuing investigations to identify the source of the package.'