Police in India are investigating the death of a Bradford businessman's father after he ate poisoned sweets on a train.

And they are examining an allegation by Kiran Singh Birk that the young wife of his 75-year-old father, Balwant, could have been involved in the death.

Harbans Kaur, 46, has been told by the Indian police that she cannot go back to England until they have concluded their investigations. They are awaiting the results of a post-mortem examination and toxicology tests on Mr Singh's body.

India's Government Rail Police started a suspicious death inquiry after Mr Singh, who lived in Southall, London, died aboard the Punjab Mail train from Kolkata to Amritsar on October 10 during a holiday. His watch and wallet are missing.

His second wife, Harbans Kaur, her daughter, son-in-law and their two children, were found unconscious in the first class compartment but recovered after five hours of hospital treatment.

Police are trying to trace a male passenger who, Mrs Kaur said, had entered their carriage and gave them the drugged sweets. But they are looking into the claim by Kiran Singh, who runs a computer business from his home in Burras Road, East Bowling, that his stepmother was involved in his father's death in a bid to claim his land and money.

Kiran, 32, said: "My father was a wealthy man and owned a substantial amount of land and property in India which he wanted me and my brother to have. My stepmother had been trying to get him to put it into the names of her daughter and son-in-law for two years, but he would not agree."

He added that his father's body had been cremated within hours of his death and the ashes scattered in a river.

SC Jain, Additional Director General of the Government Rail Police, said they had received a faxed message from Mr Singh's son and were looking into its contents.

Mr Jain said: "It is a poisoning case. It is under investigation and we are keeping all options open. If we come across any evidence of murder we will act accordingly."

Mr Jain said they were trying to trace the man on the train and had spoken to someone who was with him.

He confirmed police were wanting to question Harbans Kaur and her family.

He added: "They are staying in the Singh family village of Birk and the local police have been told they will not be allowed to go until we finalise the case.

"They are not being treated as suspects but at the same time we are keeping our options open.

"If we find they are guilty they will be arrested, if we find they are innocent they will be allowed to go."

Mr Jain said they would be able to make a decision when they had the results of the post-mortem examination and toxicology tests in about a fortnight.

Detective Constable Chris Williams, of Bradford South CID, is helping Kiran by trying to get an official version of what happened through Interpol.

He said: "I am not aware of any hard evidence as yet to substantiate Kiran's claims. But it is a nasty incident.

"Druggings happen on trains in India all the time but they do not normally occur in a first class carriage as in this case."