In a freak accident at a Houston hospital, a lift shot up while a doctor was entering it, pinning his shoulders between the doors and severing his head.

A female worker left with the severed head inside the lift for 15 minutes was being treated for shock.

Authorities were investigating what went wrong at Christus St Joseph hospital in Houston on Saturday, which killed Dr Hitoshi Nikaidoh.

"That kind of accident is almost nonexistent. There are a whole bunch of safeguards to prevent the elevator running without the doors being closed," elevator expert Charles Buckman said.

Nikaidoh, a resident who was on duty, was planning to become a Christian missionary, the Houston Chronicle reported.

He was born in Japan and was voted by his classmates at University of Texas-Houston Medical School as epitomising the qualities of a good doctor.