Staff at Abbey Insurance Brokers in Derry’s Diamond/Shipquay Street were not evacuated before Saturday’s bomb blast.
Employees at the business, which is located opposite the targeted Santander Building Society, building were horrified when they heard the blast at lunchtime on Saturday.
They emerged from the premises as the dust settled to find that the surrounding area had been evacuated.
Manager Eilish Friel said the staff had no idea that anything was going on until the bomb went off.
She said that staff had pulled the shutters on the building at 12pm as usual but remained in the building with the lights on as the office acts as the NI call centre for Abbey until 3pm each Saturday.
“The staff were horrified and shocked after they realised what had happened.
“When they looked out everything had been evacuated.”
A police spokesperson said that a review of the evacuation would be carried out.
Insp Yvonne McManus said: “It is unfortunate that these were the only premises that were not evacuated in time before the device exploded.
“We are in no doubt that this despicable act was set to injure or maim innocent members of the public and it is due to the efficient evacuations set in place in the surrounding areas that no-one came to any harm.
“We must be thankful that no one was seriously injured or killed by this explosion which happened on the busiest day of the week.”
“As with all serious incidents Police will conduct a review of their actions and procedures and where Police actions can be improved they will be.”