A woman killed her children in Spain because she feared they would be taken away, Sky sources have said after it emerged their father is one of Britain's most wanted criminals. The bodies of five-year-old Rebecca Smith and Daniel Smith, aged 11 months, were found at Hotel Miramar in the resort of Lloret de Mar on the Costa Brava 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 Friday, more than two years after he failed to answer bail in the UK. He was extradited on Tuesday and remanded in custody when he appeared at court in Carlisle Wednesday charged with 13 sex offences, including rape and child sex abuse. Sky News crime correspondent Martin Brunt said Smith's extradition may have sparked the sequence of events leading to the children's deaths. 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." Shortly before the alarm was raised, a sign had been put on the door of Ms Smith's hotel room which said: "Do not disturb, my kids are ill." The father, 45 and from North Shields, was described by Cumbria Police as being "distraught" when told of his children's death. "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. "They are believed to have left the country via Dover and may have travelled to Spain, however could be anywhere in Europe." The results of post-mortems are expected within the next 24 hours. A psychological evaluation is also being carried out on Ms Smith. She went to reception shortly before 2pm on Tuesday and emergency services were called. Efforts to save Rebecca and Daniel failed. Describing the scene outside the hotel on Tuesday, Sky's Ursula Errington said the atmosphere was "subdued". She added: "There are still two seals on the door of room 101 signed by the director-general of the Ministry of Justice of Catalonia stopping anyone going in." Source: Sky News