Which preposition to use with unannounced

into Occurrences 2%

I replied, stepping unannounced into the room.

on Occurrences 2%

The presence of these mute servants is generally no more heeded than that of our cats and dogs; but I now learnt that Martial ideas of delicacy forbid them, even as human servants would be forbidden, to intrude unannounced on conjugal privacy.

in Occurrences 1%

He seems quite at home here, and as if he were accustomed to turning up unannounced in this way.

to Occurrences 1%

The meeting between the two cousins was very long, and when Mrs. Mountjoy at last returned unannounced to the room she found her daughter in tears.

Which preposition to use with  unannounced