Police in Northern Ireland are investigating a report that an indecent image appeared for a brief period of time while Super Mario Bros Movie was screened for children recently.

The incident happened at Londonderry's Waterside Theatre on Friday, reports BBC.

It is believed that primary-school-age children were present at the event.

It is believed an image of a partially undressed woman appeared on screen for several seconds before being removed, reports BBC.

The theatre apologised for the incident.

"Waterside Theatre is aware of an unfortunate but serious incident happening today," the theatre posted on Facebook.

"The welfare of our visitors is always our main concern and we will be working with the relevant authorities. We offer our sincere apologies to all those affected," read the statement.