Are Mondays dangerous?

Is it true that more people die of heart-attacks on Mondays more than any other day of the week? I’ve also heard, through possibly slightly less than reliable sources (the British tabloids have a habit of stretching the truth rather) that more cases of genuine illness occur on Mondays too. Is this just lies based on the fact that malingerers (understandably) choose Monday as their further day of rest, or is there some substance in what I have heard?