The OSPCA says Toronto Humane Society shelter will remain closed indefinitely. (Chris Young/Canadian Press)

The beleaguered Toronto Humane Society is being investigated by the Ontario Ministry of Natural Resources over suspicions it may have violated provincial laws on the release of raccoons.

Officials from the ministry arrived at the River Street shelter Tuesday morning with a warrant to search the building.

Under provincial law, the society is supposed to release any raccoons in its custody to within one kilometre of wherever they were found.

But the ministry has reason to believe that has not been happening and wants to have a look at the society's paperwork , said Kevin Strooband, chief investigator for the Ontario Society for the Prevention of Cruelty to Animals.

"The reason that that law came into effect is because of zoonotic diseases — rabies, specifically, because rabies can be transmitted to humans," Strooband said.

"And of course, if you release a raccoon 50 miles away, now you've effectively spread that rabies 50 miles in a matter of how long it takes you to drive there."

Investigators with the ministry refused to talk to reporters.

Shelter closed indefinitely

Meanwhile, the OSPCA is still investigating the shelter, where around 1,000 animals live. The OSPCA insists it can manage caring for the animals, thanks to an increase in the number of volunteers.

But Strooband said it will remain closed to the public indefinitely.

"It may take three weeks to go through all the information in this building — it may take longer, it may take less," he said. "But our goal is still to open as soon as possible to the public so we can find homes for these animals."

None of the animals can be adopted while the OSPCA's investigation is underway.

The OSPCA, working with city police, raided the Toronto shelter last Thursday and said it found animals in such poor health that four had to be put down. Five senior officials, including the society's president Tim Trow, were arrested and charged with animal cruelty.

The Toronto Humane Society has dismissed the OSPCA's charges, calling them politically motivated. There has been a long-running feud between the two animal-care organizations.