US defense contractor personnel at the Balad Air Base in Iraq are preparing to evacuate over “potential security threats,” Iraqi military sources said Friday.

Nearly 400 contractors with the companies Lockheed Martin and Sallyport Global that are stationed at the Balad Air Base north of Baghdad will be departing the country in two stages amid rising tensions with neighboring Iran, Iraqi military sources told the media Friday.

Contractors at the base are engaged both in training and in support services, including security, life support, and other basic operations. They also help the Iraqi Armed Forces maintain their fleet of F-16 Falcon fighter jets. However, contractor conduct at the base has been brought under severe scrutiny as of late, with both the US Government Accountability Office and the US Department of Justice investigating misconduct there, including mismanagement, bigoted abuse by contractor staff, and the possibility that former Iraqi Prime Minister Nouri al-Maliki might’ve been bribed to award lucrative contracts at the base.

The US also evacuated hundreds of non-emergency diplomatic staff from its Baghdad embassy last month, citing unspecified threats from Iran, according to ABC.

Last Friday, several mortar shells landed inside the base, lighting brush afire but not injuring anyone. On Monday, three rockets fired from a Katyusha system landed in Camp Taji, northwest of Baghdad, where US troops are stationed. Then on Wednesday, a rocket that Iraqi police said was fired from a Katyusha fell about 100 meters short of the ExxonMobil headquarters it was aimed at in the southern Iraqi city of Basra. No one has claimed responsibility for the attacks.US to Initiate Evacuation of Balad Base in Iraq Over ‘Potential Security Threats’