Aid worker Linda Norgrove was killed by US grenade

Aid worker Linda Norgrove was killed by a grenade thrown by a US special forces soldier sent to rescue her, a joint US-UK investigation has found.

Ms Norgrove, 36, from Lewis, Scotland, was taken hostage in Afghanistan in September. She died on 8 October.

It had been thought she was killed by her captors.

Foreign Secretary William Hague said US soldiers had been disciplined for not informing commanders immediately that the grenade was a suspected cause.

He revealed the results of the probe in a statement to the House of Commons.

An investigation team of 10 staff spent almost three weeks in Afghanistan interviewing all involved in the rescue attempt.

They also had access to video footage, reports and post-mortem examination results which showed Ms Norgrove died of "penetrative fragmentation injuries" to her head and chest.

Mr Hague said: "After the investigation it is clear that these injuries were caused by the grenade."

He said US special forces had not immediately notified officers further up the chain of command about the grenade.

Mr Hague said this was in breach of military law and a number of soldiers had been disciplined.

Before making his statement, Mr Hague met with the Scottish aid worker's parents John and Lorna Norgrove.

In a statement, the family said: "We are grateful to have been briefed in detail by the UK and US military officers who led the inquiry into Linda's kidnapping and subsequent failed rescue attempt.

"We would like some time to digest this and the contents of the report before we make any further comment.

"We will issue a statement early next week and would ask the media to respect our privacy in the meantime."

US Central Command said Ms Norgrove's death was a terrible tragedy and those who kidnapped her were ultimately responsible for her death.

Commander Gen James Mattis added: "Ms Norgrove was a remarkably valiant young woman whose courage and compassion were well known to the Afghans she was there to help.

"Her dedication to humanitarian service - and the support of her family - have been an inspiration to us all."

Mr Hague said that with the agreement of the prime minister he had agreed to a rescue bid because of fears that Ms Norgrove's life was in "grave danger".

He said an incredibly difficult operation was launched by highly experienced personnel in extreme mountain terrain at night.

After being dropped off by two helicopters, one of two teams moved along a narrow ledge and came under attack.

Mr Hague said it was believed Ms Norgrove was being held in buildings higher up a mountain.

Gully grenade

He said: "A grenade was thrown by a member of the rescue team who feared for his own life and those of his team towards a gully from where some of the insurgents had emerged.

"When the grenade was thrown no member of the team had seen, or heard, Linda Norgrove."

Linda Norgrove's funeral was held on Lewis in the Western Isles

Following the operation Ms Norgrove's body was found in the gully.

She had been working for American-based aid organisation Development Alternatives Inc (DAI).

Louis Susman, the US ambassador in the UK said: "Our thoughts and prayers are with the family and friends of Linda Norgrove as we continue to mourn her tragic death.

"Her life of service to others was an inspiration to us all.

"Her work with Development Alternatives, Inc., an American company working for the U.S. Agency for International Development, was the latest example from a long career around the world devoted to improving the lives of those less fortunate.

"We admire the strength and devotion of Linda's parents, who have established a foundation in her memory to ensure that the communities and initiatives that she gave her life to support will not be forgotten.

"The Norgrove family is an inspiration to us all as we remember and mourn this extraordinary woman."

Ms Norgrove was kidnapped in the Dewagal valley in the Kunar province on 26 September while looking into the development of agricultural projects in the east of Afghanistan.

Her funeral was held on Lewis in the Western Isles.

An inquest into her death was opened and adjourned by Wiltshire coroner David Ridley in Salisbury in October.