The investigator, T.J Ward, has worked as lead investigator in the Natalee Holloway case, among others.
A spokesman for Bishop Long would not comment.
The news comes as the attorney of Long's four accusers appeared on several national television morning shows on Wednesday. Attorney B.J. Bernstein told television show hosts that she's ready to move forward with the case.
"We want depositions. Take the depositions of the men and have the bishop under oath and we will see," Bernstein said.
Bernstein also said the young men were disappointed that Bishop Long told his congregation during his first Sunday sermon since the lawsuits were filed that he feels like David against Goliath, because their lawsuits use the same wording.
During Long's second visit to the pulpit since news of the lawsuits broke, he preached that these difficult times are not about him.
"You're not touching me. You're messing with a holy order that God is establishing and God can handle Eddie Long," he shouted, over the congregation's applause.
Long has denied the allegations through his attorneys, but publicly he has said little other than he will fight the charges.
A former neighbor of one of accuser Anthony Flagg said he believes the young men are telling the truth. Felix Crawford said he noticed Flagg driving several fancy cars.
"I saw him in a Mustang. I've seen him in a Navigator. I seen him in a Range Rover," Crawford said.
He said he thought Flagg was involved in illegal activity until news of the sex allegations broke. The lawsuits claim that Long gave the young men cars, homes, jewelry and trips.
"I don't think a teen would put themselves out like that, and their family, and embarrass themselves like that," Crawford said.