More than 2,000 people who live near the Buncefield fuel depot have been evacuated from their homes.
As the fire continues to blaze at the facility on the outskirts of Hemel Hempstead, nearby residents are now sheltering at a leisure centre.
Residents from the Barleycroft and Leverstock Green areas have been taken to the town's Jarmans Park centre.
Police told them to evacuate in case there were further explosions at the fuel site.
Around 50 families had asked the council for overnight accommodation and are being put up in bed and breakfasts.
Two of the residents now in the leisure centre are Dominic and Sheila Gizzie, who live only a quarter of a mile from the blast site.
Many people lived very close to the fuel depot
"We got woken up this morning with a huge explosion," said Mr Gizzie.
"We have a lot of damage, our fireplace was blown out, several doors came off and the garage door has broken.
"The flames were 100ft into the air, I have never seen anything so big."
Helen Glass, from Leverstock Green, was sheltering at Jarmans Park with her two children Megan, nine, and William, six.
"There was just a massive explosion and a long rumbling sound - at first I thought it was a gas explosion or that a plane had crashed," said the 26-year-old.
"Both children came running into my room and were absolutely terrified."
Hertfordshire Chief Constable Frank Whiteley thanked local residents for their "forbearance, patience and good humour".
He said everything was being done to ensure they got all the support they required.
"The fire is likely to continue for the next 24 hours or so," said Mr Whiteley.
"It is likely that schools in and around Hemel Hempstead will be closed tomorrow.
"Libraries and day centres are also likely to be affected."