Britain’s supermarkets, wholesalers and hauliers were struggling on Thursday to ensure stable food and fuel supplies after an official health app told hundreds of thousands of workers to isolate after contact with someone with COVID-19.

Coronavirus cases in Britain have been broadly rising for a month, with more than 44,000 recorded on Wednesday.

British newspapers carried front-page pictures of empty shelves in supermarkets. Reuters reporters said food items were widely available in London shops although there were some shortages of bottled water, soft drinks, and some salad and meat products.

“We’re very concerned about the situation,” Business Secretary Kwasi Kwarteng told Sky when asked about reports of empty supermarket shelves in some areas. “We’re monitoring the situation.”