The stepfather of two missing children in Nova Scotia’s Pictou County says he took a polygraph test to help the police investigation. It is believed six-year-old Lilly Sullivan and four-year-old Jack Sullivan were last seen the morning of May 2 at their home on Gairloch Road in Lansdowne Station, N.S. Since then, investigators say they have chased down every lead. The RCMP says the investigation is still active and confirms officers have interviewed 54 people, conducted polygraph tests and received close to 500 tips – but there is still no sign of the missing siblings. Polygraph test The children’s stepfather, Daniel Martell, says he was the first to volunteer for a polygraph. “I know it would be a big help in the case and kind of narrow down maybe some of the speculations and just provide more evidence,” said Martell. RCMP Cpl. Guillaume Tremblay confirmed to reporters Wednesday afternoon that some of the 54 people interviewed in the case had taken polygraph tests. “There’s multiple facets to those investigations and those experts are examining every question and answer that those individuals are providing and it could guide the investigation,” said Tremblay. Police have not said how many tests were administered, who took the tests, or what the results were. During his polygraph test, Martell says he was asked whether or not he was involved in the disappearance of the children. He adds his cellphone was confiscated and searched by investigators, along with the cellphone of his estranged wife. Chris Lewis, CTV’s policing expert and a former polygraph examiner for the Ontario Provincial Police, says it’s significant the RCMP has administered polygraph tests. “You don’t do polygraph tests and waste that resource on people that maybe just saw something or heard something or is a real remote suspect. That’s not the way it works,” Lewis told CTV News Wednesday. “If they are doing polygraph tests and examinations on people, those are people they suspect might be involved in some way or for whatever reason aren’t being honest.” ‘I have nothing but time to just think’ At this point, there has been no major break in the case. Martell says the silence inside his once busy home is deafening. “Going from a family of seven to just me, I have nothing but time to just think,” he said. The emotional toll has left its mark on Martell, who has lost of custody of his daughter Meadow. “I haven’t even got to see my own kids, not even Meadow yet, but I’m still hopeful. I have supervised visits coming up with CPS,” said Martell. The children’s stepfather says he’s grateful for the investigators and the people who continue to share tips. He adds the family remains hopeful the children will return home safe. “It’s kind of mind-boggling that there’s not been any evidence at all,” he said. “I appreciate every tip, but it kind of leaves a lot of room to the imagination of what really went on. “I just want everybody to focus outward. Focus on the kids. The kids are the main priority, and that’ll never change.” Police across Canada involved in investigation Police say more than 11 Nova Scotia RCMP units are working on the case, along with the National Centre of Missing Persons, Canadian Centre for Child Protection, and provincial and municipal police agencies across Nova Scotia and Canada. Police say the information gathered during the investigation, including all ground search and rescue efforts, has not identified any new search areas at this time. The RCMP first launched an extensive air and ground search for the siblings, which covered 5.5 square kilometres of heavily wooded and rural terrain, shortly after they were reported missing. The search, which involved hundreds of people, dogs, drones, divers and helicopters, was scaled back five days later. Additional searches took place on May 8, 9, 17, 18, 31 and June 1. In the latest search, 78 trained searchers from across the province focused on specific areas around Gairloch Road and a nearby pipeline where a boot print was previously found. Anyone with information about the missing children is asked to call the Northeast Nova RCMP Major Crime Unit at 902-896-5060. To remain anonymous, contact Nova Scotia Crime Stoppers, toll-free, at 1-800-222-TIPS (8477). For more Nova Scotia news, visit our dedicated provincial page