A family went missing after the father made a baffling call to 9/11 in which he spoke about the 9/11 attacks and the CIA.
Anthony and Suzette Cirigliano, both 51, vanished along with their sons, Brandon, 19, and Noah, 15.
They disappeared on Sunday and are believed to be in a silver 2005 Toyota Sienna minivan, police said.
Officers said there had been no activity on any of the family's bank accounts and Anthony's phone appeared to be switched off.
Suzette's and the boys phones were found at their home in Michigan, while police said they found no other evidence as to what had happened.
The night before the family vanished, Anthony made a call just after midnight, in which he spoke to officers about the September 11 attacks.
Police spent 45 minutes speaking to Anthony and Suzette before determining nobody was in danger.
Fremont Police Department Chief Tim Rodwell said: "Anthony was complaining of some elaborate issue in regard to the Sept. 11 attack.
"He was displaying to my officers paranoia and some concerns in regard to the FBI and CIA."
Rodwell said investigators were "very concerned", adding: "The circumstances are strange.”
Anthony works in finance, and Suzette had been caring for her elderly mother, who has dementia, reports the New York Post.
Suzette had arranged no care for her mother, who was found wandering the streets of Fremont the day after they were reported missing.
An officer who spoke to Anthony and Suzette the night before they vanished said: "They seem like really good people who were taking care of their family.
“No one has had any problems with them.”
Rodwell urges anyone with information to contact the Fremont Police Department at 231-924-2100.
