explosion spritesheet is not working

Hi,

I want to do a simple explosion on a collision.Here is my code..

public explosion(Texture2D newTexture, Vector2 newPosition)
    {
        texture = newTexture;
        position = newPosition;
        timer = 0f;
        interval = 40f;
        currentFrame = 1;
        spriteWidth = 60;
        spritHeight = 60;
        isVisible = true;
    }


public void Update(GameTime gameTime)
    {
        timer += (float)gameTime.ElapsedGameTime.TotalMilliseconds;
        if (timer > interval)
        {
            currentFrame++;
            timer = 0f;
        }
        if (currentFrame == 32)
        {
            isVisible = false;
            currentFrame = 0;
        }
        sourceRect = new Rectangle(currentFrame * spriteWidth, 0, spriteWidth, spritHeight);
        origin = new Vector2(sourceRect.Width/2, sourceRect.Height / 2);
    }
    public void Draw(SpriteBatch spriteBatch)
    {
        if (isVisible == true)
        {

            spriteBatch.Draw(texture, position, sourceRect, Color.White, 0f, origin,1.0f, SpriteEffects.None,0);

        }
    }

during collision I am loading like this--

foreach (Enemy e in this.em.Enemies)
                {
                    if (i.BoundingRectangle.Intersects(e.BoundingRectangle))
                    {
                        explList.Add(new explosion(cm.Load<Texture2D>("Exp"), new Vector2(e.position.X, e.position.Y)));
                        e.OnHit();
                    }
                }

problem is instead of appearing one by one frames,frames are moving to the right side one by one in the rectangle.I am totally new to XNA .Pls help...........

---

dj_Fox