The FBI confirmed on Friday that it is investigating whether a Montrose funeral home paid by grieving families to cremate the remains of their loved ones instead returned to the families cement mix or another “foreign substance.”

Federal agents raided Sunset Mesa Funeral Directors earlier this month but no charges or formal allegations against the business have been filed.

On Friday, the FBI released a statement asking families who believe they were conned by Sunset Mesa to fill out a questionnaire. The bureau asked people to send an email to sunsetmesa@fbi.gov to receive a link to the questionnaire.

The FBI said it will conduct follow-up interviews with people, “that it believes may have information relevant to this investigation.” Investigators said they will also test “a select set of cremains” to determine whether they are human or something else. If the remains are human, the tests will not be able to determine whether they belonged to a particular person, though.

Because the FBI expects to receive more requests for tests than it can perform, the bureau said it is also working with Colorado Mesa University on a separate testing system for the public.

“There is a large amount of information to process and the investigation could take some time,” the FBI said in the statement.

Sunset Mesa was unique in the nation in that it also hosted a related business, in the same building, that took donated human bodies and sold them to medical research or educational institutions. An investigation by the Reuters news agency, though, raised questions about the two businesses’ practices, including an allegation from a former employee that gold teeth were removed from one cadaver and used to pay for a family vacation to Disneyland.

State regulators suspended the funeral home’s license this month after investigating an incident where Sunset Mesa allegedly provided a family with purported cremains that later tests determined were actually cement. When regulators searched Sunset Mesa on the same day as the FBI raid, they saw bags of cement mix, according to the suspension order.