The first post sent from the Twitter account @DimiMascarenhas read: "Geoff miller is a complete knob. He had no clue what he is doing. Fing prick."
A second said: "Chairman of selectors came to Liverpool and didn't even come and say hi ... what a prick. Doesn't take much to say hello, does it."
Both messages do not appear on the Twitter feed anymore, the Guardian website reports.
Last week Pietersen had launched a foul-mouthed tirade on Twitter when he was dropped from the England One-day and Twenty20 squads.
Pietersen will face an official hearing after publishing a tweet that read: "Done for rest of summer! Man of the World Cup T20 and dropped from the T20 side too...its a f*** up!!!."
Mascarenhas, who does not have a central contract with England, last played for England in a Twenty20 match against India more than a year ago and currently plays for English county side Hampshire, New Zealand Herald reports.
The all-rounder played for the Otago Volts last year.
An ECB spokesman said: "We are aware of the tweet and we are investigating the matter."