The fire broke out at the Centrebus depot off Spittlegate Level before 4pm this afternoon.
Newark firefighters joined collegues from Grantham, Sleaford and Stamford at the blaze on Tollemache Road South, Grantham.
Crews used breathing apparatus and hose reels to extinguish a number of buses that are on fire.
Residents were advised to keep doors and windows closed.
Six buses were destroyed.
The cause is being investigated.
Photos by R.S. Mortiss