TORONTO - Sorrow turned to frustration for volunteers at an Ontario animal shelter Wednesday as an escalating protest to end the euthanization of hundreds of cats and dogs continued to fall on deaf ears.

Demonstrators held signs with "Murder" and "I'd rather be a stray than sent to the OSPCA" printed in bold letters across stark white boards. Some chanted "Stop the killing," as a police cars descended on the area.

The Ontario Society for the Prevention of Cruelty to Animals maintains it has no choice but to destroy close to 350 animals at the Newmarket, Ont., facility, blaming an outbreak of an especially aggressive strain of ringworm.

"A few days ago I was proud to be an OSPCA volunteer, but I am not today," Ruth Wozniak said when reached at home. Wozniak has been volunteering at the shelter five-days-a-week for 10 years.

On Tuesday, Wozniak wept as she spoke about the animals' death sentences. Her sadness had turned to frustration by Wednesday.

"How are we feeling? We're feeling desperate," said a furious Wozniak, who added she has been fielding calls from upset people wanting to adopt the animals.

Two protesters were issued trespassing notices and were arrested after crossing a fence onto the property. York Regional Police said they were released with a ticket.

Ringworm, a skin infection caused by a fungus and marked by circular lesions and hair loss, can spread rapidly and experts say it is difficult to obliterate in facilities with many animals -- though the condition is not lethal.

The OSPCA has said the euthanization is necessary to stop the infection from spreading in the community.

The volunteers said the animals appear healthy, many still running around, going on walks and eating their food.

"It's hideously sad, when you perceive to see a healthy dog being put down," said Kathy Clark, another volunteer at the shelter.

Clark has been working with one dog named Marley, and said she's heartbroken to think the animal is slated to be killed.

"When she's really happy and pleased and looking at you, she has this very wrinkly face, and when I think about that wrinkly face's devastating," said Clark, pausing to maintain her composure.

In some cases, animals already approved for adoption will be euthanized.

The would-be pet owners have been turned away from picking up their animals, said Clark.

The mass euthanization brought renewed calls from the Opposition at the provincial legislature for the government to intervene.

Premier Dalton McGuinty said he understands that it is difficult for some, but said people must trust the OSPCA's decision.

"It's very painful for those who have to watch from the sidelines, but I think we have to have confidence in our experts," said McGuinty.

Frank Klees, the Conservative member of provincial parliament for the riding where the shelter is located, said the government should stay the society's decision.

The government said it does not have authority over the body.

Veterinarians were also mobilizing in an effort to stop the euthanization.

Mark Cole, a veterinarian from the Abbotsford Animal Hospital in nearby Aurora, Ont., has joined with others in his profession in hopes of finding an alternative to what he called the "permanent and drastic" decision made by the OSPCA.

Cole said he is able to organize enough of his colleagues to set up a mobile clinic across from the shelter, to perform examinations on individual animals ready for adoption.

"There was a big outcry, a lot of people wanted to adopt these animals and we thought we might facilitate that," said Cole.

He has not heard back from the society.

An OSPCA official told media outlets on Tuesday that about 20 animals would be spared from euthanization, and other animals may be euthaniazed on a case-by-case basis.

No one from the society was available for comment on Wednesday.

The society blames the outbreak on human error. Protocols for identifying ringworm in animals were not followed, but the oversight was not wilful, it said.

Six staff members were also infected as was a family member of one of the employees, which prompted fears from the society that the infection could become a public health concern.

The branch will undergo a thorough cleansing and an inspection to ensure the ringworm is eradicated before it reopens for adoptions, the society said.