A significant cluster of Covid-19 cases in the Rhondda Cynon Taf area has been linked to a coach trip of people travelling to Yorkshire, despite some of the group awaiting test results.
Health minister Vaughan Gething said some of those involved had symptoms of coronavirus, but had not received test results when they went on the outing.
The group were on an annual trip to Doncaster Races but did not have tickets to the event and did not enter the site – instead visiting a number of pubs before returning to south Wales.
Contact tracers are still working to identify people who may have been contacts of the positive cases, the Welsh Government said.
Mr Gething said the trip was a “real example of a Covid spreading event that should not happen”.
On Thursday, Public Health Wales reported three deaths of people with coronavirus, the first recorded in the country since August 31.
A lockdown came into force in Rhondda Cynon Taf at 6pm on Thursday.
Mr Gething previously said that two significant clusters in Rhondda Cynon Taf were associated with a rugby club and a pub, as well as the group taking a coach trip to Doncaster.
It is understood that the Doncaster trip, which took place over the weekend, involved a group of social club members staying in the town.
“The annual trip went ahead despite not having tickets, some members of the trip had symptoms and had taken a Covid test, drinking in pubs without waiting for test results,” Mr Gething tweeted.
“Doncaster trip members should have been from the same extended household to follow the rules on close contact. People with symptoms should be self-isolating.
“It’s a real example of a Covid spreading event that should not happen.”
Under the new restrictions in Rhondda Cynon Taf, people must not enter or leave the area without a reasonable excuse.
Meetings with other people indoors are not allowed, including for extended households. People must work from home where possible.
All licensed pubs, bars and restaurants in the borough, which has a population of about 240,000, will have to close at 11pm.
Andrew Morgan, leader of Rhondda Cynon Taf County Borough Council, said there had been about 350 new cases of coronavirus in the area in the past 12 days, about 200 of which were in the past five days.
He said about 1,500 people had been asked to self-isolate as it was believed they had come into contact with a Covid-19 case.
“The situation is starting to snowball,” Mr Morgan said.
On Thursday, 168 new cases of coronavirus were reported by Public Health Wales, bringing the total number of confirmed cases to 20,048.
Of these cases, 34 were in Caerphilly, which has been under lockdown since last Tuesday, and 32 were in Rhondda Cynon Taf. There were 18 in Cardiff, 11 in Blaenau Gwent and nine in Newport.
Dr Robin Howe, incident director for the Covid-19 outbreak response at Public Health Wales, said it welcomed the new restrictions in Rhondda Cynon Taf.
“These measures are essential to protect people’s health and control the spread of the virus,” Dr Howe said.
On Thursday, the Welsh Government announced a variation on travel restrictions for those arriving in the country.
From 4am on Saturday, those arriving in Wales from Guadeloupe and Slovenia will have to self-isolate for 14 days. However, those coming from Gibraltar and Thailand will no longer need to quarantine.