clatter from engine on start up

I have a 2001 tdci focus, which make a clattering or rumbling noise on start up which goes away within a couple of secound and runs fine, the noise seems to get worse the warmer the engine is , and normaly first thing in the morning the noise is not present.can any one please advise me on this fault.

after starting up it goes way

The noise is only present inititaly after starting and lasts only a few secounds, how ever as you use the car through out the day the engine natuaraly gets warmer, this when starting the engine warm the noise is alot noisier than when starting from cold ,hope this know makes more sense.