TORONTO (Reuters) – Canadians crossing into the United States for fuel and other essential supplies will be exempt from having to show a negative COVID-19 test result on their return, as Ottawa seeks to help flood-hit residents in British Columbia, a federal official said on Sunday.

While the flood situation in Canada’s westernmost province remains serious, there have been some improvements as water levels drop and roads and highways reopen, Bill Blair, minister of emergency preparedness, told a media conference. But more potentially damaging weather is forecast for the province this week.

Blair said the exemption would allow people living in a border community who travel to the United States for essential goods to return without the requirement of a PCR (polymerase chain reaction) test.

British Columbia declared a state of emergency after a phenomenon known as an “atmospheric river” brought a month’s worth of rain in two days, paralyzing parts of the province, leading to food and fuel shortages.

The flooding has killed at least four people and could become one of Canada’s worst natural disasters.

The province has imposed an 8-gallon (30-litre) limit for fuel purchases for non-essential vehicles.

More rain, wind and snow are forecast for the province’s North Coast regional district, which includes Haida Gwaii, an archipelago off the northern Pacific coast, through Monday, potentially causing flooding and landslides.

Last week’s flooding washed out roads and railways, cutting off Vancouver, Canada’s third-biggest city, and the lower mainland region from the rest of the country, and blocking access to some towns entirely.

Canadian Transport Minister Omar Alghabra said he is optimistic that the rail corridor will be reopened by midweek, based on feedback from rail operators.

Some 500 Canadian troops will be in the province by Sunday night to help with rescue efforts.