A Putney mother who was thought to have died after drinking water spiked with ecstasy by her son had no trace of the drug in her body, police have revealed.

Her 15-year-old son was arrested on suspicion of the manslaughter of his mother following the incident at their home. He has since been released on bail after being questioned by Scotland Yard detectives.

The boy was alleged to have crushed a tablet of the dance drug into a glass of water, intending to offer it as a prank to his 11-year-old sister.

It had originally been believed the 39-year-old mother, who takes medication for multiple sclerosis, accidentally drank the concoction on May 12 and died, having suffered a severe reaction. The allegations about ectasy being a contributory factor in the death were widely reported in the press. However a Scotland Yard spokeswoman revealed the results of toxicology tests did not support the theory.

She said: "There was no trace of ecstasy found in the woman's blood and we are awaiting results to further toxicology tests."