Six buses have been damaged during a "significant" blaze at Potters Bar Bus Garage.
A large plume of smoke was pictured over Potters Bar, and Hertfordshire Fire and Rescue Service received around 73 emergency calls about the blaze.
A spokesperson for the fire service said they received the first calls at 2.36pm today (Sunday, May 22).
Potters Bar High Street (A1000) was shut when emergency crews arrived at the blaze.
Andy Hopcraft, Hertfordshire Fire and Rescue Service's deputy chief fire officer, said: "The service was called to reports of a significant fire at Potters Bar Bus Garage at around 2.30pm this afternoon.
"The first fire engine was on the scene within four minutes, where four buses were well alight.
"Neighbouring properties were quickly evacuated and the surrounding buildings and other buses were protected from fire.
"At the height of the fire, eight engines were in attendance, and a total of six buses were on fire - two electric-hybrid, and four diesel-powered.
"Thanks to the efforts of the firefighters involved, the fire was contained to six buses and did not spread to cause further damage to other buildings or vehicles."
Mr Hopcraft added: "Although this is a significant incident, we would like to reassure residents that we are ready to respond to other emergencies if required.
"The cause and origin of the fire is currently under investigation and is yet to be established."
The fire service said Hertfordshire Police, UK Power Networks and Affinity Water were in attendance.
Fire cover was maintained throughout the county, a spokesperson said.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here