Ceilings have collapsed and a car has been crushed by a fallen tree during heavy rain and thunder storms.
The two-storey ITS building in the Britannia Centre in Lenthall Road, Debden, has been evacuated after rain water reportedly overwhelmed guttering and leaked through the roof at around 1pm.
A tree was also seen falling on a car at the site, which accommodates around 40 employees.
James Martin, a graphic designer at the company, said: “I was sat working when I saw a trickle of water coming through the ceiling and then noticed rain coming through the closed window.
“Then it just started gushing.
“About 10 minutes after the rain had started coming down a tree fell on my colleagues’ car.
“It was chaotic.
All Mr Martin’s work from today will be lost due to the “calamity”.
Colleagues acted quickly and are in the process of salvaging what they can from the offices.
Mr Martin added: “Everyone here has been great and been helping with brooms and water pumps – it’s that sort of company.”
Two fire crews from Loughton attend the incident.