The Kildare offices of the Equestrian Federation of Ireland were broken into in another twist to the Irish Olympic gold medal controversy.
Federation president Avril Doyle said a cabinet had been rifled.
The latest twist comes after a police investigation was launched into the theft of a doping test sample of Cian O'Connor's horse Waterford Crystal.
"It may be an ordinary break-in, but I am afraid the coincidence is rather too much," said Ms Doyle.
''In the context of an international investigation involving Lausanne in Switzerland and Cambridgeshire in the UK, this is not just your ordinary
break-in.
''The front door of the offices had been forced, an internal office broken into and a cabinet rifled
through,'' she added.
The break-in came just hours after equestrian bosses sought an urgent meeting with the Federation Equestre Internationale after the ''B'' sample belonging to Waterford Crystal went missing.
O'Connor requested the result of a ''B" sample after his horse's positive test at the Games.
The FEI said the "B" sample had been "taken illegally" while en route from Paris to a laboratory near Cambridge.
The FEI also said it had started an internal investigation.
The sample was being shipped by a third-party courier service from the Medication Control Programme Central Laboratory in Paris to the Horseracing Forensic
Laboratory in Cambridgeshire.
O'Connor risks being stripped of the gold medal for his victory in the individual show jumping event in Athens. Both O'Connor and his vet, James Sheeran, have continuously protested their innocence in the matter.
Despite the missing sample, the FEI added that the "medication control case" was going ahead.
O'Connor became a national hero after winning Ireland's only Olympic medal at the games and the
country's first ever in an equestrian event.
After the banned substance was found in Waterford Crystal's sample, it later emerged that a second of his horses had failed a drugs test. The same sedative appeared in a sample taken from ABC Landliebe at an event in Rome.
But O'Connor insisted that he had not cheated and said he had nothing to hide.
On Monday, Ms Doyle said that the whole saga was worrying. "At this stage there are more questions than answers. But I don't like what I'm hearing," she said.