Disk in ASM is full but is not accessed

Hello everybody...

I have a RAC database with ASM and monitoring the phisical space I found that one disk is full and is not being accessed. why could it happend?  and what could I do to clear it or recover that space..?

SQL> select GROUP_NUMBER,PATH,MOUNT_STATUS,TOTAL_MB,FREE_MB,HEADER_STATUS from v$asm_disk where group_number=0;

GROUP_NUMBER   PATH                                             MOUNT_S         TOTAL_MB             FREE_MB         HEADER_STATU
  ------------                   ----------------------------------------      ----------                ----------                     ------------             -----------------------
  0                                /dev/rdsk/emcpower21a              CLOSED            8627                        0                          FOREIGN