The ammunition was accompanied by a threatening letter.
The move has been branded 'disturbing.'

The employees were said to be shocked when the ammunition was delivered to their workplace on Friday morning.

Police remarked: "We have seized a number of items for forensic examination. We never comment on issues relating to the security of any individual.

It's been reported that the bullets were sent to staff who have relatives serving in the security forces.

SDLP Foyle MLA Mary Bradley says those responsible are "faceless cowards."

"This is understandably a very disturbing case for those concerned and my first priority is the safety and wellbeing of those who have been targeted.

"To single out relatives of security force members in this manner is a throw back to the bad old days of the Troubles that the majority in this community had hoped we had left behind."

A spokesperson for Ulster Bank declined to comment on the matter "at this time."