Is the above sentence correct?

Looks technically correct. Is there a part you are concerned with?

The victims may have then been asked to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.
The victims may have then been asked to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.

...may have then been asked...
I think the above part is not quite right.

While I prefer your example, here are five more ways this thought can be expressed and still retain the same meaning:

1. Then the victims may have been asked to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.

2. The victims then may have been asked to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.

3. The victims may then have been asked to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.

4. The victims may have been then asked to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.

5. The victims may have been asked then to pay administrative fees, legal fees or taxes in order to encash their profits, the police said.

Thanks, hightor!