Contact the ISP to whom the IP addresses are registered, through a lawyer. Tell them that the laptop is stolen and ask them to confirm in writing that they could produce the name and address of the person using those IP numbers at the given time, if required to by law.
They don't need to give you that info, just confirm that they have it.
Then you can approach the police showing them that the only thing they need to do is obtain a subpoena for the info from the ISP to resolve the case.