One of two twin babies rushed to hospital in a life-threatening condition last week has died.
Lincolnshire Police issued a statement today saying that one of the twin boys, who are both under one, has lost his fight for life.
Police say they are keeping an open mind around the cause of death.
Officers were placed on guard outside a house in Granville Street, Boston, after the children were taken to hospital.
A 27 year-old-man and a 20 year-old-woman were arrested and released on bail, police said last week.
Details of the incident were originally released by the force last Thursday after the twin boys were taken to hospital separately with life-threatening conditions.
A spokesperson said at the time: "We received a report that a boy was taken to hospital seriously ill at around 5pm on March 27. Later the same day, we received a report that this boy’s twin brother was also seriously ill and taken to hospital.
"Both remain in hospital.
"At this stage it is unclear if these children have suffered a medical episode and investigations are ongoing to establish the circumstances."
Detective inspector Lee St Quinton said last week: "This is clearly a sensitive case for the family involved.
"We are working closely with the family at this difficult time to establish the facts of the matter."