button placed on top of UIVisualEffectView not responding

I'm trying to add a button to UIVisualEffectView. However, the button that I add is not responding to touch events and I don't understand why. This is the code.

override func viewDidLoad() {
        super.viewDidLoad()
        let image = UIImage(named: "face2")
        let imageView = UIImageView(image: image)
        imageView.frame = CGRectMake(0, 0, 200, 200)
        let button = UIButton(frame: CGRectMake(50, 50, 100, 100))
        button.setTitle("huhuhu", forState: UIControlState.Normal)
        button.setTitleColor(UIColor.blackColor(), forState: .Normal)
        button.userInteractionEnabled = true

        let effect = UIBlurEffect(style: .Light)
        let blurView = UIVisualEffectView(effect: effect)
        blurView.frame = view.bounds

        view.addSubview(imageView)
        view.addSubview(blurView)
        view.addSubview(button)
    }