Based on Anand comments, I figured out the way to do so:
$term = get_term($_GET['catId'],'product_cat');// first parameter is the cat ID
$args = array( 'post_type' => 'product',
'posts_per_page' => -1,// unlimited posts
'product_cat' => $term->name,// Pass the category name
);
More info here: http://codex.wordpress.org/Function_Reference/get_term