The Mangaung local municipality's head office in Bloemfontein was closed on Thursday for the day when the Scorpions Unit seized the Bram Fischer building in terms of a search warrant.
Scorpions head in the Free State Lebo Mdalana said the raid formed part of an investigation into fraud and corruption relating to tenders by high ranking municipal officials.
She said the search started on Thursday morning at the houses of six officials.
No indication was given to the identities of the officials or the specific tenders being investigated.
Mdalana said that they were not expected to make any arrests on Thursday.
Kopung Ralikontsane, acting city manager, confirmed that National Prosecuting Authority officials had spent the day searching and seizing "certain information and documents.
"The particulars and details of the exercise are at this stage not known to the municipality."
He indicated however that normal activities should resume at the Bram Fischer building on Friday.
Free State opposition parties have welcomed the Scorpions action.
Democratic Alliance leader Andries Botha said his party recently asked the auditor-general to investigate tender transactions, and also requested the Public Protector to look into the property transactions of the municipality. - Sapa