Over 20 police officers are self-isolating after a colleague who attended a retirement bash tested positive for coronavirus.
Lancashire Police said the officer displayed symptoms of Covid-19 after attending the party in Blackburn with eight others.
The gathering was three days after Blackburn with Darwen Council warned a lockdown might be necessary.
After contact tracing, 22 officers began self-isolating, the force said.
A Lancashire Police statement said: “We can confirm some police officers based in Blackburn are self-isolating after a colleague tested positive for Covid-19.”
“An officer developed symptoms and was tested on 21 July.
“Immediately after we were notified of the positive result, rigorous contact tracing was put into place which has resulted in a number of officers self-isolating.
“These staff will progressively return to work depending on when the contact with the affected officer took place.”
Assistant Chief Constable Peter Lawson said: “We take the health of both our officers and the communities we serve extremely seriously.
“I can reassure people that we continue to meet all our minimum staffing levels and there will be no effect on operational policing in the county.”