Why ieeeconf.cls makes the titles of theorems, definitions, lemmas, etc. bold with roman numbers

I am using the formal ieeeconf.cls and am using the amsthm package. When I define the following,

> \newtheorem{theorem}{Theorem}[section]
> \newtheorem{proposition}[theorem]{Proposition}
> \newtheorem{corollary}[theorem]{Corollary}
> \newtheorem{lemma}[theorem]{Lemma}
> \newtheorem{algo}[theorem]{Algorithm}

e.g., title of theorem becomes bold with a roman number but I want it to be like all common papers which are not bold but they are italic with normal numbers. I know I can modify the class manually to do that but I wonder the usual ieeeconf.cls behaves like this for me.

Any help would be appreciated. Thanks.