Image caption Mr Primrose was said to be in good health when he was found

Briton Malcolm Primrose, who was kidnapped in Indonesia on Tuesday, has now returned to his family, the oil company he works for has said.

Medco E&P also expressed its "deepest gratitude" to the local authorities after the release of the 61-year-old oil engineer, who was seized in the north Sumatran province of Aceh.

Indonesian officials say an extensive hunt for his captors is continuing.

A police spokesman said Mr Primrose was found on Thursday in good health.

He was found alone at a security post inside a palm oil plantation, East Aceh district police chief Lieutenant Colonel Muhajir told the Associated Press news agency.

Earlier, police had said the Briton, originally from Stirling, had made contact via telephone and his kidnappers had asked for a ransom.

Image caption Aceh has a history of separatist conflicts and violence

But the spokesman said no money exchanged hands, and police and the military were still looking for the men who had kidnapped him.

Officials there believe the motive for the kidnapping was a grudge against the Indonesian company Mr Primrose worked for.

He and his driver were returning to their base camp on Tuesday when their car was ambushed by four armed men. The driver was tied up while Mr Primrose was driven away by the abductors.

Mr Primrose has worked for several oil and gas companies in the Aceh region as a drilling expert since 1981, a statement from Medco E&P said.

Aceh is a resource rich and strongly Muslim province that has had a history of separatist conflicts and spates of violence - sometimes targeting foreigners.

In 2009 there were shootings involving some foreigners but police say there have been no known kidnappings of Westerners in the province in recent years.