Dev env files created in Prod env - symfony

Question

I'm running my symfony2 project in prod environment, I've executed :
rm-rf app/cache/dev
rm-rf app/cache/prod
When I visit one of ma pages (cache created), I find files in dev folder.
the folders created are:
Can you explain why to me.
This is my config file
Config.yml
imports:
- { resource: parameters.yml }
- { resource: security.yml }
- { resource: services.yml }
framework:
profiler:
enabled: true
#esi: ~
#translator: { fallback: "%locale%" }
secret: "%secret%"
router:
resource: "%kernel.root_dir%/config/routing.yml"
strict_requirements: ~
form: ~
csrf_protection: ~
validation: { enable_annotations: true }
templating:
engines: ['twig']
#assets_version: SomeVersionScheme
default_locale: "%locale%"
trusted_hosts: ~
trusted_proxies: ~
session:
cookie_lifetime: 43200
# handler_id set to null will use default session handler from php.ini
handler_id: ~
fragments: ~
http_method_override: true
salva_jshrink:
flaggedComments: true
# Twig Configuration
twig:
debug: "%kernel.debug%"
strict_variables: "%kernel.debug%"
# Assetic Configuration
assetic:
debug: "%kernel.debug%"
use_controller: false
bundles: [ ]
filters:
cssrewrite: ~
# Swiftmailer Configuration
swiftmailer:
transport: smtp
# transport: "%mailer_transport%"
# host: "%mailer_host%"
# username: "%mailer_user%"
# password: "%mailer_password%"
spool: { type: memory }
# app/config/config.yml
doctrine_mongodb:
connections:
default:
server: mongodb://user:password#127.0.0.1:27017
options: {}
default_database: database
document_managers:
default:
auto_mapping: true
metadata_cache_driver:
type: memcached
class: Doctrine\Common\Cache\MemcachedCache
host: localhost
port: 11211
instance_class: Memcached
web_profiler:
toolbar: true