The crisis in Iraq has prompted U.S. contractors with personnel there to evacuate them from areas near Baghdad that are increasingly in the line of fire as insurgent fighters capture more territory with the apparent end goal of seizing the Iraqi capital.

The individuals are being “temporarily relocated by their companies due to security concerns in the area,” State Department spokeswoman Jen Psaki said in a statement Thursday evening. The individuals involved include U.S. citizens who are currently working under contract with Iraq’s central government in support of the Pentagon’s foreign weapons sales program.

Psaki did not mention the number of personnel affected, but it could be hundreds, if not thousands, of people. The Pentagon oversaw 6,624 contractors in Iraq in October, including 1,626 Americans, according to a quarterly report released at the time. The number plummeted to 0 as the Defense Department transferred oversight of those contracts to the Baghdad government, but it is believed that many of the individuals involved stayed in Iraq and continued their work.

The move came as security in Iraq continued to crumble as a powerful faction of insurgent fighters with the Islamic State of Iraq and Syria, an extreme offshoot of al-Qaeda, seized control of more territory north of Baghdad and set their sights on taking over the capital. They’ve swept through the region since capturing Mosul, the largest city in northern Iraq, on Monday.

Contractor evacuations began Wednesday, if not earlier, said Ginger Cruz, CEO of Mantid International LLC, a consulting firm that works with numerous companies in Iraq. In one example, health-care provider CHS Middle East initiated evacuations from Balad Air Base, some 40 miles north of Baghdad.

CHS was awarded a multi-year contract in April to provide medical services on the base under the Pentagon’s foreign military sales program as Iraq prepares for the arrival of its first F-16 fighter jet later this year from the United States, according to a CHS news release published in April. The company was expected to provide emergency care, dental work, surgery and other medical services to as many as 2,500 personnel living on the base, the news release said.

On Thursday, the electronics giant Siemens was working to get about 50 employees out of Baiji, Cruz said. It was not clear exactly what their operation there entails, but the company announced in February that it had signed a deal to provide service and maintenance to a large gas power plant there. The oil refinery city is some 130 miles north of Baghdad.

Cruz said that her firm has recommended using teams of U.S. and Kurdish private security firms to evacuate the contractors because the semi-autonomous Kurdish government in Iraq’s north had sent its security forces known as pesh merga to take control of the city of Kirkuk after Iraqi security forces abandoned their bases and equipment and fled. The Kurdish forces now control roads in the region.

Negotiations were ongoing to secure the safety of foreign personnel in Baiji and to get them out of harm’s way. U.S. security contractors involved reported that they engaged in gunfire to get through the region, Cruz said.

U.S. personnel at the U.S. Embassy in Baghdad remained at work, Psaki said Thursday night. The State Department said in January that it had about 5,000 personnel working at the embassy and at consulates in Basra and Irbil, including 2,000 Americans. Embassy personnel are protected by some 200 Marine Corps security guards and contractors who work from a $10 billion, 5-year Worldwide Protective Services contract the department signed with eight companies in 2010.

The companies involved in the protective services deal include defense giants like Dyncorp International and Triple Canopy. Dyncorp also signed a five-year deal with the State Department in 2010 that could be worth up to $894 million to provide a fleet of aircraft, including UH-1 utility helicopter and DHC-8 planes.

Senior staff writer Karen DeYoung contributed to this report.