FBI reaching out to users of the defunct QuadrigaCX cryptocurrency exchange

The FBI has stepped up its investigation into the spectacular demise of the Vancouver-based QuadrigaCX cryptocurrency exchange.

The victims services section of the FBI has posted a survey on its website asking potential victims to disclose details about their account balances, transactions and other financial records.

QuadrigaCX was one of Canada's largest cryptocurrency exchanges before it was shut down amid a storm of controversy in January.

Last month, the accounting firm trying to recover more than $200 million in missing cash and cryptocurrency confirmed it had found only $28 million in assets, virtually all of it in cash.

The FBI says it is legally mandated to identify victims of the federal crimes that it investigates and provide them with information and assistance.

The American investigation includes resources from the Internal Revenue Service, the U.S. Attorney's Office for the District of Columbia and the computer crime section of the federal Justice Department.