Officials say propane space heaters used at Happy Cat Sanctuary in Medford have not been ruled out as the cause of Monday's devastating fire. The owner, Christopher Arsenault, was killed, along with nearly 100 cats. “The official cause will be listed as undetermined, can’t rule out the propane-fed space heaters in the area of origin," said Brookhaven Town Chief Fire Marshal Chris Mehrman. Suffolk County Police Department's arson unit says the cause of the fire is still under investigation. A flood of people - including rescuers and well-wishers bringing supplies - went to the sanctuary Tuesday to help. Rescuers believe around 100 cats died, with 200 surviving. There is an effort to help the surviving cats. A GoFundMe page was started and already has raised more than $640,000 to pay for vet bills.