Police officers work on a crime scene after eight people believed to be illegal immigrants being smuggled into the United States were found dead inside a sweltering 18-wheeler trailer parked behind a Walmart store in San Antonio, Texas, US July 23, 2017. [Photo/VCG]

HOUSTON - Eight people were found dead in a trailer carrying illegal immigrants at a Walmart parking area in southern Texas City of San Antonio early Sunday morning, authorities said.

The San Antonio Police Department said the victims include at least two children, adding that about 30 more people were found inside the truck and were transferred to local hospitals for treatment.

Police did not know the victims' country of origin, destination, or ages of the deceased or injured, it said.

San Antonio is a US city close to the border area with Mexico. Border Patrol agents have reported an increase in smuggling attempts in tractor-trailers in recent weeks, starting with 44 people from Mexico and Guatemala discovered after police stopped an 18-wheeler on June 19 near one of the city's international bridges.

On July 7, the agents found 72 people from Mexico, Ecuador, Guatemala and El Salvador inside a locked trailer in the same part of town. The next day, they found 33 people from Mexico and Guatemala inside a trailer stopped at a Border Patrol checkpoint.

In another incident last week, border patrol agents found 16 people inside a locked trailer.