McALLEN — No one has been charged a day after nearly 20 migrants were discovered inside a trailer in Edinburg, according to officials with Homeland Security Investigations.

But the investigation into who is responsible for leaving 17 people locked inside a tractor-trailer in rural Edinburg continues, according to HSI officials.

“HSI continues to pursue leads to determine who is responsible for this criminal act. Right now, no one has been charged. The investigation continues,” HSI spokeswoman Nina Pruñeda said Monday.

Edinburg Police received word just before noon Sunday from a relative of one of the migrants who said they had been trapped inside the locked tractor-trailer for more than eight hours with no water or relief from the heat.

When officers arrived at the Flying J truck stop at 1305 East Monte Cristo Road in rural Edinburg, they began pounding on the trailers in the parking lot and heard them pounding back, Edinburg police officials said.

Police believe the 17 people, who did not require medical attention, hail from Guatemala, Honduras, Mexico and Romania.

The temperature reached 102 degrees in Edinburg around noon, according to the National Weather Service.

Before being taken into custody, The Monitor observed a group of more than 10 individuals sitting in a shaded area underneath a tree.

Police detained a Cuban adult man and woman, whose names were not released, but are believed to be responsible for the tractor-trailer. Their status remains unknown as of Monday afternoon. It is not clear who the driver of the tractor-trailer was.

Pruñeda said late Sunday HSI special agents would continue to work with local and state law enforcement officials to determine who was responsible for leaving the group locked inside the tractor-trailer.

The discovery of the migrants locally comes three weeks to the day that 10 undocumented migrants died and another 20 suffered serious injuries after being discovered inside a tractor-trailer in the parking lot of a Wal-Mart in San Antonio.

On July 23 law enforcement officials found 39 men, women and children trapped inside a trailer after they were left inside for an unknown number of days.

The driver of the tractor-trailer in that case, 60-year-old James Matthew Bradley Jr., of Clearwater, Fla., faces several federal charges in connection with the deaths.

In a news release late Monday afternoon Thomas D. Homan, Immigration and Customs Enforcement acting director, said sanctuary cities are one of the many pull factors that perpetuates human smuggling.

“In just a few weeks since the tragedy in San Antonio that claimed the lives of 10 aliens during their transport in a tractor trailer by a criminal smuggling operation, we’ve seen three more of these cases in the same area. While additional loss of life has been avoided thus far, these cases underscore the urgent need to remove pull factors like sanctuary policies that only perpetuate the vicious human smuggling cycle. We will not let up in our efforts to disrupt and dismantle the illicit pathways used by transnational criminal organizations and human smuggling facilitators.”