Papers from a inquiry which criticised the way Brecon Beacons National Park handled a planning application have been handed to Dyfed-Powys Police.
The park says issues raised by the inquiry are being tackled
The park said the matter was in the "hands of the police to investigate any pattern of wrong-doing".
The independent inquiry was launched following complaints about the way an application for a caravan park near Brecon was dealt with.
Dyfed-Powys Police confirmed they had met officials from the national park.
The inquiry, commissioned by the park, found documents about the caravan park application at Gilestone Farm in Talybont-on-Usk, near Brecon, were missing from a file.
It also found problems with the park's complaints procedure and made 29 recommendations.
The chief executive of the national park Christopher Gledhill said: "We were so concerned by the findings resulting from the Gilestone report that we asked Powys Council's internal auditors to investigate.
"It is now in the hands of the police to investigate any pattern of wrong-doing."
Dyfed-Powys Police said officers had met the national park, but would not comment further at the moment.
Since the inquiry into Gilestone there have been calls for the national park to be stripped of its power to grant planning permission.
On Thursday, a meeting between planning consultants, developers and the park it was claimed companies were losing money because park planners were taking too long to process applications.
The park said changes were being made to planning services.