shadowMap cant detect all instances on THREE.InstancedBufferGeometry - three.js

Question

I'm implementing something similar to the buffer geometry instancing dynamic example.
Basically the idea is having one bufferGeometry duplicated and having an attribute array with the offsets of my objects (like they have in the above example).
If I try to add shadows, I only get shadows on 1 object, which I assume is because we only have 1 geometry.
Is there a way of adding shadows to all my objects?
var scene, camera, renderer, controls;
var offsets;
init();
animate();
function init() {
scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 1, 10000);
camera.position.set(0, 250, 1000);
renderer = new THREE.WebGLRenderer();
renderer.shadowMap.enabled = true
renderer.shadowMap.type = THREE.PCFSoftShadowMap
renderer.gammaInput = true
renderer.gammaOutput = true
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
controls = new THREE.OrbitControls(camera, renderer.domElement);
// Lights
var ambient = new THREE.AmbientLight(0xcccccc);
scene.add(ambient);
var spot = new THREE.SpotLight(0x999999, 1, 0, Math.PI / 2, 1);
spot.position.set(700, 700, 700)
spot.target.position.set(0, 0, 0);
spot.castShadow = true
spot.angle = Math.PI / 4
spot.penumbra = 0.05
spot.decay = 2
spot.distance = 10000
spot.shadow.mapSize.width = 1024
spot.shadow.mapSize.height = 1024
spot.shadow.camera.near = 1
spot.shadow.camera.far = 10000
scene.add(spot);
var spotHelper = new THREE.SpotLightHelper(spot)
scene.add(spotHelper);
// Floor
var geometry = new THREE.PlaneGeometry(3000, 3000, 10, 10);
var material = new THREE.MeshPhongMaterial({
color: new THREE.Color(0x777777),
shininess: 5
});
var ground = new THREE.Mesh(geometry, material);
ground.rotation.x = -1.57;
ground.receiveShadow = true;
scene.add(ground);
// instanced geometry
var instances = 10;
var geometry = new THREE.InstancedBufferGeometry();
var icosahedron = new THREE.BufferGeometry().fromGeometry(new THREE.IcosahedronGeometry(200, 3));
geometry.addAttribute('position', icosahedron.attributes.position);
geometry.addAttribute('normal', icosahedron.attributes.normal);
geometry.addAttribute('uv', icosahedron.attributes.uv);
geometry.setIndex(icosahedron.index);
offsets = new THREE.InstancedBufferAttribute(new Float32Array(instances * 3), 3, 1);
var vector = new THREE.Vector3();
for (var i = 0; i < offsets.count; i++) {
var x = Math.random() * 1000 - 500;
var y = Math.random() * 1000 - 500;
var z = Math.random() * 1000 - 500;
vector.set(x, y, z).normalize();
offsets.setXYZ(i, x + vector.x * 5, y + vector.y * 5, z + vector.z * 5);
}
geometry.addAttribute('offset', offsets);
var material = new THREE.ShaderMaterial({
uniforms: {},
vertexShader: document.getElementById('vertexShader').textContent,
fragmentShader: document.getElementById('fragmentShader').textContent,
side: THREE.DoubleSide,
});
var mesh = new THREE.Mesh(geometry, material);
mesh.castShadow = true;
mesh.receiveShadow = true;
scene.add(mesh);
}
function animate() {
requestAnimationFrame(animate);
renderer.render(scene, camera);
}
Example JsFiddle