A patient has been taken to hospital and Northamptonshire Police are attending an ongoing incident in Duston.
The incident happened in Sam Harrison Way on the Timkin estate just after lunchtime today (Friday) when East Midlands Ambulance Service were called to deal with a medical emergency.
An eyewitness said that the air ambulance landed on the football pitches nearby.
Michael Boeg said: "This started at 11.30am and it's still going on.
"No-one was allowed to go anywhere.
"People wanted to come down and walk their dogs but they were not allowed.
"An air ambulance was called and landed in the football field."
A spokeswoman for East Midlands Ambulance Service said: "We received a call at 12.16pm today to Sam Harrison Way, Northampton to assist with a medical emergency.
"We sent two paramedics in two ambulance cars, a crewed ambulance and the air ambulance.
"We transported one patient to Coventry and Walsgrave General Hospital."
Northamptonshire Police have been contacted for comment but have not yet responded.