Pharmaceuticals giant GlaxoSmithKline has told thousands of staff to turn off the NHS Covid-19 app while at work.
It told them to switch off the Bluetooth contact-tracing feature at its research-and-development labs and some of its manufacturing sites.
GSK, which is working on a vaccine for the virus, said it had "strict Covid protective measures at all our sites".
But some "are distinct from the everyday situations in which most people will use the NHS Covid-19 app".
"Our pharmaceutical laboratories and manufacturing plants are highly controlled environments and operate according to the highest Covid-19 security and protection protocols set out by the government," GSK said.
"Employees who have chosen to download the app should continue to use it in the normal way when they are not working in these highly controlled Covid-secure environments."
GSK said this was in line with government advice.
Some staff spent time working behind plexiglass or wearing personal protective equipment (PPE).
And all were told to remain 2m (6ft) apart.
But the app, which has been downloaded more than 16 million times, does not register a risk contact unless two people are closer than 2m for 15 minutes or more.
And in the frequently asked questions section of its guidance, the government specifically addresses the question of what to do if workplaces are deemed to be Covid-secure, saying the app is still an important tool in the fight against the virus, helping the NHS track where and how quickly it is spreading.
Hull-based Rix Petroleum has also asked staff to switch off Bluetooth, which is used by the app to notify people if they come into contact with someone who tests positive for coronavirus.
The company's managing director described it as a "blunt weapon".
"Large numbers of people who are not sick will be made to stay off - or it will be suggested that they should stay off - for 14 days," he told BBC News.
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