Image shows a white border underneath

Well, I made a button and within this button , I put an img. On the site, the image has a white border under it. I already took the border of the button through CSS and still it continues. Which property is giving the edge? I want to remove it.

Note: It only appears below.

HTML Code:

<article id="almoco">
<header class="categoria">Almoço</header>
<figure>
<button>

Image CSS:

  img {
        max-width: 100%;
    }

Button CSS:

  button {
        background-color: #FFFFFF;
        border-style: none;
    }