The mother and son hurt in an Interstate 65 pileup Monday afternoon have died, authorities said Tuesday.

Rebeccah F. Fourness, 38, and her 4-year-old son were hurt after a semitrailer smashed into a line of three cars slowed for traffic near the Ind. 10 exit in Jasper County, about four miles south of the Lake County line.

Fourness was airlifted to Loyola University Medical Center in Maywood, Ill., where she died, Indiana State Police said. Her son, David W. Fourness, died at the University of Chicago Hospitals Comer Children's Hospital at 2 p.m., said a spokesman for the Cook County medical examiner's office.

The semitrailer rear-ended the vehicle in which the mother and son were traveling about 1:15 p.m. in the interstate's northbound lanes, Indiana State Police Cpl. Chad Woody said. Investigators were unsure Monday why the semitrailer did not stop in time, he said.

The wreck turned into a pileup. John Huhn, 44, of Westfield, and his passenger, Jim Gaskins, 42, of Indianapolis, were taken to nearby hospitals with cuts and pains, Woody said.

Semitrailer driver Lozano Wilfredo, 40, of Oak Forest, Ill., was not hurt, Woody said.

The wreck blocked the highway's northbound lanes for hours.