OTTAWA—The president of the Public Health Agency of Canada has been given until the end of the week to explain why two Canadian government scientists were let go 18 months after being escorted from Canada’s only Level 4 laboratory. Iain Stewart came under fire Monday from opposition MPs after he repeatedly refused to explain why PHAC terminated the employment of Dr. Xiangguo Qiu and her husband, Keding Cheng, in January. Stewart told the special committee on Canada-China relations that he could not provide details due to privacy issues and “security with respect to the investigation” still being conducted by the RCMP. He would say only that PHAC conducted its own investigation, that it is now completed and the pair are no longer employed by the agency. “I’m not at liberty to discuss it further,” Stewart said repeatedly. The pair were escorted out of the National Microbiology Laboratory in July 2019 …