Splitting Phaser CE with Webpack?

I'm using Phaser CE with Webpack, but the bundle gets huge (3.4Mb!). It's probably not built to use modular. Is there a way to split it?

// main.js

"use strict";

import 'pixi'
import 'p2'
import Phaser from 'phaser'

import BootState from './states/Boot'
import SplashState from './states/Splash'
import GameState from './states/Game'

import config from './config'

class Game extends Phaser.Game {
  constructor () {
    super(config.gameWidth, config.gameHeight, Phaser.AUTO, 'phaser_stage', null)

    this.state.add('Boot', BootState, false)
    this.state.add('Splash', SplashState, false)
    this.state.add('Game', GameState, false)

    this.state.start('Boot')
  }
}

window.game = new Game()

// webpack.config.js

var path = require("path");
var webpack = require('webpack');

// Phaser webpack config
var phaserModule = path.join(__dirname, '/node_modules/phaser-ce/')
var phaser = path.join(phaserModule, 'build/custom/phaser-split.js')
var pixi = path.join(phaserModule, 'build/custom/pixi.js')
var p2 = path.join(phaserModule, 'build/custom/p2.js')

module.exports = {

    entry: {
      "main": "./app/main.js",
      "challenge1": "./app/challenge1/main.js"
    },

    output: {
        path: path.join(__dirname, "web/js"),
        filename: '[name].bundle.js',
        chunkFilename: '[id].chunk.js'
    },

    plugins: [
      new webpack.optimize.CommonsChunkPlugin({
        name: "vendor",
        minChunks: Infinity,
      })
    ],

    module: {
        rules: [
          { test: /pixi\.js/, use: ['expose-loader?PIXI'] },
          { test: /phaser-split\.js$/, use: ['expose-loader?Phaser'] },
          { test: /p2\.js/, use: ['expose-loader?p2'] }
        ]
    },

    node: {
      fs: 'empty',
      net: 'empty',
      tls: 'empty'
    },

    resolve: {
      alias: {
        'phaser': phaser,
        'pixi': pixi,
        'p2': p2
      }
    },

    watch: true
};

// webpack output

               Asset       Size  Chunks                    Chunk Names
challenge1.bundle.js    3.37 MB       0  [emitted]  [big]  challenge1
      main.bundle.js  391 bytes       2  [emitted]         main
    vendor.bundle.js    5.78 kB       3  [emitted]         vendor
   [1] (webpack)/buildin/global.js 509 bytes {0} [built]
   [2] ./app/challenge1/config.js 3.82 kB {0} [built]
   [3] ./app/main.js 285 bytes {2} [built]
   [4] ./app/challenge1/main.js 556 bytes {0} [built]
  [11] ./app/challenge1/states/Boot.js 323 bytes {0} [built]
  [12] ./app/challenge1/states/Splash.js 1.91 kB {0} [built]
  [13] ./app/challenge1/states/Game.js 5.38 kB {0} [built]
  [14] ./app/common/numberutils.js 588 bytes {0} [built]