Three airlines in South Africa took the unusual step of grounding some planes Tuesday after a regulator flagged compliance issues and ordered maintenance checks. Things got weirder when no one would publicly say exactly what needed checking.

The groundings by state-owned South African Airways and its Mango unit, plus Comair Ltd, which operates British Airways domestic flights and low-cost carrier Kulula, were big local news. There were some delayed and rescheduled flights.

The disruptions followed Civil Aviation Authority inspections at South African Airways Technical, the maintenance provider for the airlines. But what specific violations the inspectors found, and whether they compromised passenger safety, remain a mystery.

“The audit results revealed findings that put into question the airworthiness status of the said aircraft,” the transport ministry said in a statement, adding that compliance issues were identified without being more specific.

A spokeswoman for the aviation authority said in an interview with Cape Talk radio station Wednesday that aircraft were signed off by workers for SAA Technical who weren’t authorized or qualified to do so.

In a separate interview on SAfm radio, CAA Director Poppy Khoza said the authority’s recent audit found no evidence “at this time” of faulty parts in circulation at the maintenance provider. SAA Technical recently denied local media reports alleging it uses defective parts on aircraft it services.

“SAA Technical has since submitted a corrective action plan aimed at addressing the irregularities,” the transport ministry said. The move by the aviation authority was an act of precaution, Transport Minister Fikile Mbalula said at late-day media conference.

Comair said its fleet was fully operational Wednesday morning.