The OSPCA has said there is no expiry date on its search warrant for the Toronto Humane Society animal shelter. (Canadian Press)

A judge in Toronto has ruled employees of the Toronto Humane Society can go back inside the shelter next week.

Workers have been barred from entering the shelter on River Street since late November, when the Ontario Society for the Prevention of Cruelty to Animals (OSPCA) executed a search warrant on the building, the Toronto society says.

The OSPCA raided the building on Nov. 26 and arrested and criminally charged five top Toronto Humane Society (THS) officials with cruelty to animals.

The humane society had been fighting to quash the warrant that led to the investigation and for staff who weren't criminally charged to be allowed into the building.

While Tuesday's ruling is a partial victory — 35 THS staff will be able to enter the shelter on Dec. 29 — areas housing animals will remain under the control of the OSPCA as it continues to investigate what one official called a "house of horrors."

The staff members who have been allowed to enter the shelter are mostly senior managers who do finance and administrative work, said society laywer Frank Addario.

But it is unclear when — or if — the society will be able to put up more animals for adoption.

Investigation has continued for 4 weeks

The Toronto Humane Society alleged the search warrant had overreached its original mandate.

In documents filed in Ontario Superior Court, society lawyers said the judge was initially told the search would only take five days, not the four weeks it has now stretched into.

"The OSPCA has effectively used the search warrant to seize control of the operations of the THS, and has repeatedly frustrated the ability of the THS to maintain its operations and business by denying THS employees access to essential THS records and computer systems," THS lawyers wrote.

The THS claims the continuing investigation violates employees' Charter rights.

The humane society has also decried the public nature of the OSPCA's investigation. The OSPCA has been very public in its investigation, holding news conferences, providing updates to reporters and conducting a media tour of the shelter.

"It can reasonably be said that this type of conduct is unprecedented. Counsel can locate no case in which a professional investigator has behaved comparably," THS lawyers wrote