Perception = Reality
There's also an accusation, which Fox's office disputes I should point ou, that the government pressured local officials not to tell families sooner that the miners likely had died instantly. There's a Reuter's story on it that appeared in the Washington Post.
While it's a tough issue for government leaders on how to respond when there's a tragedy, the one main principle in crisis communication is that perception equals reality. If the peopleperceived he didn't do enough, then he didn't do enough.
Russian President Vladamir Putin was also harshly criticized when the Kursk submarine sunk killing its crew. The difference, however, is that Putin was on vacation and stayed on vacation during the tragedy. Worse, he refused help of other countries until it was way too late.
Another main principal in crisis communication is that the first step should be empathy. It looks like his office did do that by expressing condolences. I found a press release on the Mexican government site. However, it's dated February 26.
I'm not here to judge President Fox's response one way or another. Only to say that from a public relations perspective he is suffering a major hit for not adhering to basic crisis communication principles.