The recipient, in Cascade near Grand Rapids, said her husband opened two packages - one containing a liver, the other a partial human head.

"He started the second one, but stopped as soon as we saw the ear," she told the Grand Rapids Press newspaper.

The delivery company, DHL, said it was not immediately clear what happened but the labels were reportedly in Chinese.

The company says it is co-operating with investigators.

The authorities believe 28 more bubble-wrapped human organs could have been dispersed across the country.

The body parts - which are preserved - were for medical research, police spokesman Roger Parent said.

"There will definitely be a shock to people if they see these things, but there is no hazard to health," he added.