The news was confirmed in a statement on the club's website, however there was no indication over whether Grant and Clarke would be taking over on a permanent or not.
"The club is delighted that in Avram we have an experienced man who can come in immediately at this difficult time to help deliver our objectives," read the statement.
"In Steve we have a Chelsea man and he will be a crucial part of the management team going forward. Avram and Steve have our full confidence and support."
Grant, who took Israel to the brink of the 2006 World Cup, joined the Chelsea board in the summer from Portsmouth, much to the disgust of Mourinho, who sneered at his methods and his abilities.
Mourinho bid his players farewell at Chelsea's training ground in Cobham, Surrey this morning before running past a crowd of photographers, his face hidden in his trademark trench coat. He refused to comment on his departure from Chelsea before getting into the back of a black saloon car and being driven off.
The online said he is understood to have contacted five senior players by text message last night to inform them of his departure and by midnight the entire first-team squad knew he was going. The club's chief executive Peter Kenyon, chairman Bruce Buck, and Chelsea's owner Roman Abramovich's key aide, Eugene Tenenbaum, were then called to an emergency meeting at Stamford Bridge last night to discuss the situation.
Many of Chelsea's staff and players had last night been enjoying a relaxing evening at a Fulham Broadway cinema as they watched a screening of Blue Revolution - a new documentary about the Abramovich years. But senior players like captain John Terry and midfielder Frank Lampard were absent and the remainder, except a reluctant Shaun Wright-Phillips, refused to talk to the media. Mourinho also attended the evening but also ignored the waiting media and looked decidedly glum.