Update on August 28: According to ABC TV news, the transfer of funds is underway at the present time. The dollar amount noted was $271 million from DHS; $151M is from FEMA.
From CNN: Homeland Security moves $155 million from FEMA disaster relief for immigration enforcement
Here is another take from NBC: Administration Pulling Millions of FEMA Disaster Relief to Send to Southern Border.
Recovery Diva 
FEMA has been a convenient piggy bank for Homeland Security ever since losing its status as an independent agency.