One package was found to contain white powder and a chilling note warning it was lethal.
The ground was sealed off and staff put in isolation as experts tested the powder.
Special Branch were then called in after cops read the sickening antisemitic threats against Israeli Grant, 52, and his TV star wife Tzofit, 43.
One note read: “You are a back-stabbing Jewish b*****d.
“When you open this letter you will die a very slow and painful death.”
A second message made twisted sexual threats against his wife Tzofit, adding: “Then she will die.”
Dad-of-two Grant was subjected to racist abuse after replacing Jose Mourinho as manager last September.
Many fans thought Grant – a close pal of Chelsea owner Roman Abramovich – was to blame for Mourinho’s axeing.
I checked the BBC News and Sport, Sky News and Sport, BBC teletext news and Sport and ITV teletext news and sport. None of them made any mention at all of this news item. I also looked at Google News UK and Yahoo News UK. Not a mention.