Authorities in northern Illinois are investigating after the body of the wife of a Nobel Prize-winning chemistry professor was found in a landfill, hours after the two were reported missing in Indiana.

The Ogle County Sheriff's Office said in a news release that deputies found the body of Sumire Negishi, 80, and the couple's car Tuesday at Orchard Hills Landfill in Rockford, Ill., shortly after they found Ei-ichi Negishi, 82, walking nearby. Rockford is about 160 kilometres west of Chicago.

Family members said Ei-ichi Negishi was confused and searching for help when he was found. He was apparently in "an acute state of confusion and shock," and the couple's vehicle was stuck in a ditch.

The relatives told WTHR-TV in Indianapolis that Sumire Negishi was near the end of a battle with Parkinson's disease and the couple intended to go to the airport for a trip. When the car wasn't functioning, he got out of the car to look for help.

"We are very proud of his distinguished career, but more importantly know him as a beloved and loyal husband, father and grandfather," said the family in a statement to the television station.

The sheriff's department said in a statement that foul play is not suspected, but wouldn't discuss autopsy results. The release also said Ei-ichi Negishi was taken to hospital.

The couple were reported missing Monday from their home about 320 kilometres away in West Lafayette, Ind., where Ei-ichi is a Purdue University chemistry professor.

The couple are shown at the unveiling of a bronze sculpture of Ei-ichi Negishi outside of Wetherill Laboratory of Chemistry on the campus at Purdue University in West Lafayette, Ind. (Steve Scherer/Purdue University via AP)

The Japanese scientist won a Nobel Prize in Chemistry in 2010. He is best known for his discovery of the Negishi coupling, a chemical process that has been used in the pharmaceutical industry to create asthma drugs, and he won the Nobel for "palladium catalyzed cross couplings in organic synthesis" jointly with Richard F. Heck and Akira Suzuki.

Born in 1935, he graduated from the University of Tokyo in 1958, then moved to the U.S., where he earned a PhD from the University of Pennsylvania in 1963. He became a professor at Purdue in 1979.

According to his biography on the official website of the Nobel prize, the couple met in a choir group in Japan. She was two years younger, the daughter of the choir director. They began dating in Ei-ichi's first year of university in Tokyo and were engaged to be married the day after he graduated.

The couple were respected by the academic community in which they lived.

"Purdue University and the world have lost a dear friend in the death of Sumire Negishi," Purdue president Mitch Daniels said in a statement Wednesday. "Throughout a lifetime of love and loyalty, she supported her husband in a career of tremendous contributions to science and to the teaching and training of subsequent generations of top scientists."