Crews from Cosham, Fareham, Portchester, Southsea, Eastleigh, Gosport Beaulieu, Romsey and Ringwood fire stations are tackling the blaze in a warehouse at Barwell Lane, Gosport.
A spokeswoman from the Hampshire Fire and Rescue Service said: ‘They were called at 7.30pm this evening when smoke was seen coming from a building.
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‘The incident is ongoing.’
A Fareham resident travelling from Portsmouth along the M27 said the ‘huge’ smoke plume from the fire could be seen from the motorway.
She said: ‘Several fire engines passed us on the motorway.
‘We drove past the fire and there was a huge amount of smoke.
‘There was so much black smoke we couldn’t see properly.’
Gosport police took to social media to warn people about the on-going incident, calling for anyone in the area to ‘steer clear’ as emergency services attend the scene.
The post said: ‘We are currently at the scene of a serious fire at a business premises on Barwell Lane, off the A32.
‘Please avoid the area. If you live nearby, please ensure you keep all windows and doors closed for your own safety.’
Further updates will be provided as the incident develops, according to the spokeswoman from the fire service.