The decision was made after the Iraqi government refused last week to renew the firm's operating license because of a 2007 incident in which the Iraqi government says security guards -- then employed by Blackwater -- fired on and killed 17 Iraqis.

CNN: Official: U.S. will not renew Iraq contract with Blackwater

The area was sealed off immediately after the incident but flights were reported to be operating normally in and out of the airport.

BBC: Mexico City airport shootout leaves three police dead

He added that the guards involved in the incident were still in Iraq and were co-operating with the FBI investigation.

BBC: NEWS | Middle East | Blackwater guards 'were fired on'