Australian authorities say a body has been found in floodwaters and 36 military workers injured in a vehicle crash as wild weather from a tropical storm lashes the country’s eastern coast.

Cyclone Alfred was downgraded to a tropical low on Saturday but is due to make landfall near the Queensland capital city of Brisbane in coming hours.

Officials have warned residents to stay indoors and remain vigilant, saying the storm’s threat is “not over”.

Winds have brought down trees and power lines and flooded low-lying roads. More than 300,000 properties are without power in the region.

Police said on Saturday they had discovered a body in the search for a 61-year-old man who went missing on Friday after his car was caught in floodwaters in Dorrigo, northern New South Wales.

Emergency responders witnessed the man escaping his car and climbing onto a tree near the riverbank, but rescuers were not able to reach him before he was swept away.

Police found a body in the area on Saturday and said it “is believed to be that of the missing man”.

In a separate incident on Saturday, 36 military personnel were injured in a convoy crash in Lismore, about 200km south of Brisbane. One truck overturned while driving on a narrow road. A second truck then collided with it.

They had been part of military crews deployed to Lismore, near the Queensland border, to help rescue and response operations.

“Our ADF [Australian Defence Force] heroes were on their way to help Australians in need,” Prime Minister Anthony Albanese said in a statement noting some had been “seriously” injured.

Albanese earlier on Saturday had addressed the nation from the capital Canberra, saying millions of residents were “well-prepared” but “we must remain vigilant.”