It’s not far fetched to say if a lab escape did occur, it would be in the government’s best interest to keep that secret (it could easily affect reputation/blame from others).
An analogous example would be a hit and run by a drive. The driver may have driven recklessly but not have meant to do damage to others, after damage is done the driver doesn’t want to be discovered. Similarly if this was a lab escape, the government doesn’t want their recklessness to be known.
Then why did they cover up and downplay the seriousness at the start?