The pair are being investigated over a Twitter exchange which suggests they were frustrated with the pace of proceedings in an attempted murder case in a court in the Landes area of southwestern France.
"Here's a jurisprudence question for you: a prosecutor who strangles the judge in the middle of a case, how long would he get?" read the opening tweet, to which his colleague replied: "I'll stand as a character witness!"
The banter continued in a similar vein and was picked up and published by local newspaper Sud Ouest.
It could not be accessed Wednesday as the two Twitter accounts involved had been deleted since the end of the trial last
The two prosecutors have not been suspended pending the outcome of the investigation.