Washington (CNN) A team of US military and federal law enforcement forensic experts made its first visit to a suspected mass grave site near Raqqa, Syria, in recent days where the remains of executed US hostages may be located, two defense officials tell CNN.

The precise location of the site is not being disclosed because of security concerns ISIS could target the area which is currently under Syrian Democratic Forces control, the officials say.

The team is looking for the remains of American hostages, and possibly other westerners, executed by Mohammed Emwazi , the brutal British ISIS operative known as Jihadi John. He was filmed beheading multiple hostages.

Initial reports suggest it may be difficult to isolate and recover the remains of individuals because the site contains multiple areas where a large number of ISIS victims were buried. It also appears ISIS took steps to try to disguise the location months ago.

The intelligence that led the US to the site came from two British ISIS fighters captured in eastern Syria in early January, according to multiple US officials.

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