Authorities with U.S. Immigration and Customs Enforcement were contacted but declined to retrieve the suspects, District Attorney General Russell Johnson said.
"There were no state charges on which to hold the four, who were merely passengers in the operation," Johnson stated in a news release. "State and local agencies have no authority or ability to deport illegal aliens, so they were released."
Still missing: the driver and co-driver of what was Johnson called an "illegal human-trafficking operation."
Those two men, paid to transport the passengers, also are allegedly illegal immigrants from Mexico, officials said.
Ten people were in the van when it was stopped near the Sugar Limb Road exit of I-75 Monday morning.
Six of them fled on foot "in unison" when authorities with U.S. Immigration and Customs Enforcement arrived, said John Sanchez, investigator with the 9th Judicial District.
The incident sparked a massive manhunt that included police dogs and a helicopter from the Knox County Sheriff's Office.
Sanchez said Loudon County sheriff's deputies nabbed the four suspects Tuesday morning after a resident reported seeing them walking along New Providence Road.
The suspected illegal immigrants told authorities they were traveling from Texas to Knoxville, where they had been promised work in a restaurant.