An American woman died after becoming pinned under a rock when a family rafting trip on the Mohaka River in Hawke's Bay turned to tragedy yesterday.

Caroline Lackey, a 59-year-old Kentucky woman, was rafting with her husband, son and daughter-in-law when they all fell out of the raft at a section of the river known as the Te Hoe drop-off about 3pm, police said.

While the three other family members were carried downstream and managed to scramble ashore, Ms Lackey became pinned under a rock and was believed to have drowned.

Police were called about 3.30pm.

The woman's body was recovered by the Lowe Corporation rescue helicopter and taken to Hawke's Bay Hospital.

"It was a recreational rafting trip, a family one, and there were no commercial operators involved," Senior Sergeant Stuart Fleming, of Hastings, told NZPA today.

He said Taupo police were investigating the incident for the coroner on behalf of the Hastings police.

An autopsy was to be carried out tomorrow.