According to a Border Patrol press release, the van's driver parked, climbed out of the vehicle and yelled what sounded to agents like instructions.
Minutes later agents saw several individuals, all thought to be undocumented immigrants, come out of nearby brush and get into the van.
Agents followed the two vehicles to a local restaurant parking lot, where agents questioned the occupants of the vehicles. Border Patrol officials, declined to name the restaurant.
After questioning the group, the agents apprehended 23 people as undocumented immigrants, all from Mexico, and arrested the four alleged smugglers.
Three of the 23 immigrants were being held Friday as material witnesses. The remaining group members returned voluntarily to Mexico, according to the Border Patrol.
Officials said the group had entered the United States by floating down the New River, one of the nation's dirtiest waterways.
This summer the New River and the All-American Canal were listed as high-risk zones by federal authorities on both sides of the border because of the level of use of both waterways by immigrants.
Border Patrol agents said earlier this summer they see large numbers of immigrants attempt to enter the country by floating down the river each night.
Agents have said the river is used as an entry point because smugglers and immigrants know Border Patrol agents are not going to enter the waterway because it is filled with diseases.
Agents have said the immigrants can follow the river for several miles into the Valley, past frontline Border Patrol effort.
In July the New River again took center stage as four immigrants died in the river over one weekend.
Border Patrol officials have said they are starting to talk about creating a device that could be raised and lowered to block the New River at the border.
While the blocking device could not remain in the water permanently, agents could lower it into the river when they see immigrants moving toward the border.
Officials have said they have only started discussions on such a device.
Thursday's arrest of the four alleged smugglers came days after two other alleged smugglers were arraigned for reportedly leading a group of immigrants into the county. In that case, a woman that was part of the group died from heat exposure.
On Friday those two suspects were facing charges of immigrant smuggling. However, authorities said they could face stiffer charges as the investigation moves ahead.
Staff Writer Darren Simon can be reached at 337-4082.