Enterprise JavaBeans :: Does Container Managed Entity Manager Is Thread-safe In Stateless Session Bean?

I read JEE6 doc and confused with : Does container managed entity manager (injected by PersistenceContext annotation) is thread-safe in stateless session bean in multiple-thread env?
 
See code below, if there are 2 requests to stateless sesion bean in 2 concurrent threads ,  is it using same Entity Manager Instance or not?
 
@Stateless(name = "HRFacade", mappedName = "HR_FACES_EJB_JPA-HRFacade-HRFacade")
public class HRFacadeBean implements HRFacade, HRFacadeLocal {
    @Resource
    SessionContext sessionContext;
   
    @PersistenceContext(unitName = "HRFacade")
    private EntityManager em;
 
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