The Royal Mail has confirmed four postal workers at the Plymouth Delivery Office are recovering at home from coronavirus.
But it has denied claims that workplace Covid rules have not been followed at the centre in Breakwater Road, Plymstock.
A source has alleged that some post staff have been working in cramped conditions which meant they were unable to stay socially distanced.
They also claimed that measures including signs and PPE were being “rushed through” following the outbreak.
The source told the Local Democracy Reporting Service: “Although since the new cases the management have pushed face masks and have now put out PPE stations, these have been non-existent before during the pandemic. I’m just hoping it’s not a ‘too little too late’ scenario.”
A spokesperson for Royal Mail said it took the health and safety of colleagues, customers and the local community “very seriously” and ways of working had been revised to ensure staff could maintain social distancing.
They said an intensive clean of the site had taken place since the four coronavirus cases at the centre, with extra cleaning at “key touch points and all communal areas”.
The spokesperson said a range of measures were in place to protect staff and customers during the pandemic.
The Royal Mail said in a statement on Friday: “Royal Mail takes the health and safety of its colleagues, its customers and the local communities in which we operate very seriously.
“Four colleagues have tested positive for coronavirus at Plymouth Delivery Office. They are now recuperating at home and we wish them a speedy recovery.
“We have carried out an intensive clean of the site and have organised additional cleaning of key touch points and all communal areas.
“We are keeping the CWU (Communication Workers Union) and colleagues updated.
“Throughout this crisis, every decision we make puts the health of our people and customers first.
“We have put in place a range of preventive measures to protect both our customers and our colleagues.
“We were the first UK company to put in place social-distancing measures in relation to parcel delivery. We pioneered contact-free delivery. We are temporarily not handing over our hand-held devices to customers to capture signatures.
“As well as encouraging good hand hygiene, standard ways of working have been revised to ensure that colleagues maintain appropriate social distancing at all times.
“All staff have been briefed about the social distancing measures jointly agreed by local management and the CWU. This has been supplemented with visible reminders such as posters and one-way floor markings.”
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Cases of Covid-19 have been rising in Plymouth and across Devon, although the infection rate has stayed below the England average.
The latest figures on Friday showed there were 400 cases in Plymouth in the previous week, with a rate of 152.6 cases per 100,000 people, compared to the rate for England of 231.8.