Thirty-five of 55 illegal aliens discovered aboard a Houston-bound freight train were pulled from a locked boxcar where temperatures soared as high as 130 degrees inside, authorities said.

U.S. Border Patrol officials said 35 dehydrated El Salvadorans were found in the boxcar at about 11 a.m. Sunday, and another 20 aliens - 19 Mexicans and one man from Honduras - were discovered in other areas of the freight train.There were at least three teenagers among the 55 undocumented workers, all of whom were being held at the Sarita Border Patrol checkpoint deep in south Texas, authorities said.

The 35 El Salvadorans who were inside the boxcar said the door to the car was to have been kept open to allow ventilation, but either a smuggler or a train station employee in Brownsville closed and locked it, said Border Patrol agent Ramiro Gonzalez.

He said the aliens were trying to get air through small holes in the boxcar, which was "packed" with a type of fiberglass lining.

"It was well over 100 degrees (outside) when we found them," Gonzalez said. "It was probably another 20 to 30 degrees inside the car."

The National Weather Service said it reached a high of 98 in Kingsville Sunday.

The group in the boxcar included three women and two 14-year-old boys.