At least four people were killed while some others were injured when a US drone fired missiles in a house at North Waziristan Agency here on Friday, sources said. Four missiles were fired from the pilotless aircraft at a house and a vehicle suspected of carrying militants in Datta Khel area of North Waziristan, a place bordering Afghanistan and believed to be a stronghold of militants. As a result, four persons were killed while several others sustained injuries in the incident.