Investigation should normally be done calmly. What your gov did was nothing short of fear mongering, sensationalist and propagandistic. Why not reveal it once you have proof that it was Russian submarine introding into your water?
The whole thing is "officially" based on observations by "thrustworthy" civilians.
My guess, former Navy officers, living in the archipelago.
It is therefore not surprising, that the Swedish Press got hold of this early.
The government, contrary to what you claim has not said that much.
It would not be the first time, they keep information secret.
It may be that nothing was found, or a deal was made with the owner of the submarine.
Maybe a submersible robot painted a Swedish flag on the submarine as a warning,
The Press may of course get additional information through leaks. happens everywhere.
You can always accuse the press of sensationalism. Thats what they do.
With the current aggressive behaviour of Russian Armed forces and PROVED Russian
violations of Airspace of most neighbouring countries, Russian submarines inside the territorial waters of other countries would just confirm the common perception of Russia. Would not be sensational.
If Russia does not want bad press, then Russia should start to behave according to
International Law.