Contamination at a laboratory hampered an investigation into the death of a five-month old baby, an inquest heard.

Oliver-John Boswell-Parker died at Darent Valley Hospital in April after falling ill at home in Thistle Road, Denton, Gravesend.

DS Martin Carter, from Kent Police, told Maidstone's Archbishop's Palace the boy was asleep in bed with his mother and father when at around 10.30am his grandmother walked into the room and noticed a "small red foam" coming out his nose.

Desperate attempts were made to rouse him and CPR was administered until paramedics arrived.

Oliver-John was rushed to hospital but despite the best efforts of medical staff was pronounced dead just before midday.

A post-mortem was carried out at Great Ormond Street but failed to give a cause of death.

DS Carter said police began investigating because social services had been involved in his care.

The reasons for this were the baby's mum had lost her first son Jessie-Lee at the age of three months to Sudden Infant Death Syndrome and the three-bedroom house they lived in was considered overcrowded — there were 10 people living there.

Health visitors observed Oliver-John was developing well and his mum was caring for him.

DS Carter added she and the baby's father co-operated with police throughout and that third party involvement was soon ruled out.

Further tests did reveal trace amounts of cocaine and amphetamine in Oliver-John's system, although doctors confirmed the quantities were so small they would not have contributed to his death.

"Both parents were truly shocked when they found this out," DS Carter said.

"Both volunteered to do drugs tests."

No evidence of drugs were found at the property and it was suggested Oliver-John could have come into contact with the substances while in public.

However, it later transpired a breach at the laboratory meant neither sample could be relied on and therefore it was not possible to continue with that part of the investigation.

Oliver-John's mum then contacted DS Carter to tell him following a routine test she had been diagnosed with blood disease alpha-thalassemia, missed in her two previous pregnancies.

The condition has been known to result in still births and early death in infants.

However, coroner for North West Kent Roger Hatch said without any conclusive test results he was left with no option but to record an open verdict.