Firefighters joined their colleagues from the police at HMP Ranby where a disturbance involving prisoners is ongoing.
Shortly after 7.30pm around 15 firefighters arrived outside the prison and began putting on their full kit before walking in through the main gate.
Officers carrying shields and other equipment were also seen going into the prison earlier.
More top news
Nearly 750,000 people worldwide have died with Covid-19.
Marion County Sheriff Billy Woods said he had weighed both sides of the issue.
It was not until August 15 1945, days after US atomic bombs fell on the Japanese cities of Hiroshima and Nagasaki, that the battle in Asia w