An elderly woman's body donated to a medical research lab was discovered on the side of a north Texas road after falling through the back window of a transport van, police said on Friday.

The mortuary van carrying the body of Nell Joseph, 79, was headed to a Science Care facility in Colorado on Tuesday when a rear window broke and the cadaver slid out onto the highway without the driver noticing, said police in Denton, north of Dallas.

An officer found the black body bag with Joseph's remains packed in medical-grade ice during a routine patrol.

The van's cargo and passenger areas are separated by a metal barrier, which could have prevented the driver from noticing that the cadaver fell out, police said in a statement.

Joseph died from a lung disease in a Fort Worth hospital on Thanksgiving Day. Her remains were donated for the study of chronic obstructive pulmonary disease, her family told local broadcaster WFAA-TV.

Melinda Ellsworth, a spokeswoman for Science Care, said the van was carrying multiple donors but only Joseph's body fell off the vehicle. The company has suspended services with the transportation provider.

"The family still wants to go forward with the donation," she said.