Another 55,000 washing machines in UK homes should stop being used and need repairing or replacing owing to a fire risk.
An extra 21 models have been added to the list of 524,000 Hotpoint and Indesit machines being recalled.
Owners may have checked twice previously and told their machines were safe, only now to need to check again.
Whirlpool, which owns the brands said the recall programme was ongoing despite coronavirus restrictions.
Who is affected?
About 20% of the Hotpoint and Indesit washing machines sold since 2014 are affected by a safety fault and need to be recalled, a process that started in January.
Seventy-nine fires are thought to have been caused by an overheating door locking system, a fault that develops over time, according to Whirlpool.
The company said it had located 210,000 of those appliances, and had resolved 177,000 of those so far.
Now, another 55,000 have been added following further investigations. With 21 Hotpoint models added to the list, the total number of models affected is 66.
Jeff Noel, vice-president of Whirlpool, said: "With people spending more time at home under the current social-distancing measures, it's more important than ever that this safety issue is tackled swiftly.
"We are deeply sorry to our customers for the concern and inconvenience this recall may cause but we continue to take action because people's safety is our top priority."
Lesley Rudd, chief executive at charity Electrical Safety First, said: "It is alarming that five months into this recall we are only now hearing of these extra models which pose a risk to owners. This new discovery throws into question the robustness of the original investigation."
Advice for owners
Whirlpool has set up a model checker online. Owners of Hotpoint and Indesit washing machines bought since October 2014 will need to enter the model and serial number of their appliance - found inside the door or on the back - to see if it is one of those affected.
Those who have previously checked, and been given the all clear, may need to check again.
There is also a free helpline, open every day, available on 0800 316 1442.
Slots for a modification or replacement machine are available straight away.
All owners affected by the recall are entitled to a replacement washing machine or a repair to their existing appliance, without charge, but there is no offer from the company of a refund.
They should stop using it until an engineer has checked it, if necessary, restrict its use to a cold wash.
Whirlpool said engineers and delivery teams were equipped with protective equipment including face masks, gloves and hand sanitiser, and were practising social distancing at all times during their work, to allow them to continue during the coronavirus lockdown.
Customers did not need to physically sign any paperwork, and were called in advance of their scheduled delivery or repair appointment to make specific arrangements, the company added.
If requested, appliances could be delivered to a secure location outside a customer's home, such as a garage or garden, so that staff did not have to enter their home, although this would mean they would have to fit the appliance on their own.