Ms Mangan was an employee of McDonald’s in Castlebar, Co Mayo, when she was raped by her co-worker Shane Noonan at a house party in May 2013.
Shane Noonan, aged 28, of Castlehill Park, Turlough Road in Castlebar, Co Mayo, pleaded guilty earlier this year to the rape of Ms Mangan at the house party 10 years ago.
He was jailed on Monday for seven years, for what the judge described as the “cold, predatory and premeditated” rape of his work colleague as she drifted in and out of consciousness on a bathroom floor.
In the aftermath of the rape, Ms Mangan said she was subjected to “rape comments” and “rape songs” by colleagues in her then-workplace when the owner was absent.
In a statement to the Irish Independent, McDonald’s UK and Ireland chief executive officer Alistair Macrow expressed his shock at hearing that the allegations related to a McDonald’s outlet.
“I commend Ciara’s bravery in speaking about her horrific experience,” he said.
“I am deeply appalled by these new allegations, and commit to investigating them to our fullest extent through our Investigation Handling Unit.”
It is understood that the fast-food chain was not aware of any of Ms Mangan’s allegations until yesterday.
On foot of queries relating to an interview with Ms Mangan, published in today’s newspaper, and outlining in detail the abuse she suffered at work, an investigation is now underway.
The outlet in Castlebar is operated by a couple from Mayo.
The strong response from Mr Macrow comes as McDonald’s faces a raft of workplace harassment claims in the UK.
Earlier this week, a BBC report stated that over 100 current and recent UK staff have made allegations including sexual assault, harassment, racism and bullying.
Multiple workers, including teenagers, claimed that managers at outlets across the UK had been responsible for harassment and assaults, and that senior managers often failed to act on complaints.
In news reports on the scandal, Mr Macrow said there was “simply no place for harassment, abuse, or discrimination” in the company.