A woman killed her children in Spain because she feared they would be taken away after it emerged the father was one of Britain's most wanted fugitives, Sky sources have claimed.
The bodies of five-year-old Rebecca Smith and Daniel Smith, aged 11 months, were found at Hotel Miramar in the Costa Brava resort of Lloret de Mar on Tuesday.
Sky News sources in Spain have claimed mother Lianne Smith has confessed to suffocating them "with a plastic bag".
The children's father, Martin Smith, was seized in Barcelona on May 8, more than two years after he failed to answer bail in the UK.
He was extradited yesterday and remanded in custody when he appeared at court in Carlisle today charged with 13 sex offences, including rape and child sex abuse.
According to Sky News crime correspondent Martin Brunt, Smith's extradition could have been the catalyst that set the events leading to the children's deaths in motion.
Brunt said: "His removal back to the UK may have triggered this terrible tragedy.
"A source in Spain has told me that Lianne Smith said to police she was very concerned that the Spanish authorities would take the children off her."
Initial reports had suggested there were no obvious signs of violence at the scene.
Brunt added: "It looks as though a plastic bag was used to kill them - that is the latest information from Spanish sources."
Sky News has also learned a sign had been put on the door of Ms Smith's hotel room shortly before the alarm was raised which read: "Do not disturb, my kids are ill."
Sky sources: Martin Smith's extradition may have sparked the tragedy
The father, 45 and from North Shields, was described by Cumbria Police as being "distraught" when told of his children's deaths.
"It is an extraordinary twist to a very tragic story," said Brunt.
Rebecca had been reported missing on website Help Find My Child - which posts details of abducted or missing children.
In an entry dated December 7, 2007, the girl was said to be missing from Lichfield in Staffordshire.
The website says: "Police are concerned for Rebecca who has not been seen since she left the UK with her mother and father Martin Smith."
Martin Smith Had Worked As A tv psychic
Before skipping bail in 2008, Smith had worked as a TV psychic, appearing on Living TV's Most Haunted show.
According to Spanish police, another British man is still being sought in relation to the deaths.
Speaking outside Hotel Miramar, Sky News' Ursula Errington said: "We understand from Spanish media, quoting police sources, that they are looking for a British male who was not resident at the hotel."
The results of post-mortems are expected within the next 24 hours.
A psychological evaluation is also being carried out on 43-year-old Ms Smith.
She went to the hotel reception shortly before 2pm on Tuesday and emergency services were called. Efforts to save Rebecca and Daniel failed.