About 40 American service members have been rushed to the U.S. Embassy in Juba, South Sudan, as the country teeters on the verge of another civil war.

The troops will bolster security at the embassy and help non-emergency personnel leave, said Samantha Reho, a spokeswoman from U.S. Africa Command.

"This contingent brought in several vehicles solely for use in protecting the embassy," Reho said . She declined to provide any information about what military service or units the troops come from, citing operational security concerns.

" We do not discuss the specific forces involved or the specific capabilities the Crisis Response Force has available," she said. "What I can say is the CRF is a flexible and ready force that has all the tools it needs to respond to any crisis in AFRICOM's area of responsibility."

Hundreds of people have reportedly been killed in resumed fighting between rival factions loyal to South Sudan's president and vice president. Both leaders reached a tentative truce on Monday.

In response to ongoing violence , the State Department on Sunday ordered the non-emergency personnel to leave the U.S. Embassy in Juba. Any U.S. citizens in South Sudan have been advised to take precautions to enhance their personal security since the embassy's ability to provide emergency services to Americans is extremely limited, State Department spokesman John Kirby said Sunday.

In 2013, the Marine Corps added a security guard detachment at the embassy in South Sudan. Marines guard embassies' access points and safeguard classified material. They are also equipped with weapons and nonlethal tools to deal with emergencies or security breaches at embassies.

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This is not the first time the U.S. has had to send troops to Juba. In January 2014, Marines from the Special Purpose Marine Air Ground Task Force—Crisis Response—Africa helped to evacuate staff from the embassy.

The Marines used MV-22B Ospreys and KC-130s to fly nearly 4,200 miles from their base in Morón, Spain, to Juba, successfully evacuating more than 20 embassy personnel.