The Colorado State Patrol pulled over a van Friday morning that was driving too slow on the highway and discovered 16 people inside -- all of whom are suspected illegal immigrants from Mexico.

This is the third van discovered this week that is believed to be involved in human trafficking.

On Thursday, a van with 15 people inside was found when it broke down near Evergreen. On Tuesday, four people were killed and 10 injured when their van crashed and rolled on Interstate 70.

The CSP said that a trooper pulled over the third van on I-70, at mile marker 219, near the east portal of the Eisenhower Tunnel, at 9 a.m. The van was going too slowly and was holding back traffic, CSP said.

When the trooper walked up to the vehicle, he saw that there were large things blocking the windows so he couldn't see inside. That's when he had everyone walk outside, and counted 16 people.

Two people were being held for investigation and the others were to be turned over to federal immigration authorities, Clear Creek County Sheriff Don Krueger said. Their names and immigration status were not immediately available.

The minivan was eastbound and had North Carolina license plates.

The minivan that crashed during Tuesday's snowstorm was also headed to North Carolina. The driver in that crash, Jose Franco-Rodriguez, was arrested on charges including human smuggling, the CSP said.

Three men were arrested for Thursday's incident. Jorge Trujillo Gonzalez, 35; Ignacio Alejandro Hernandez-Trujillo, 30; and Reydavid Valdez Pacheco, 30, were arrested on various charges.

The Clear Creek County sheriff's deputy saw the men while responding to a call of three suspicious men near Clear Creek High School. A nearby Dodge minivan contained 12 others, sheriff's officials said.

Authorities said using minivans in human smuggling operations is relatively new. The groups had used moving trucks to transport the Mexican nationals to various parts in the country but minivans are more inconspicuous, they said.

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