Invalid characters with fromJSON function

Question

I am trying to import json file into R. For the purpose I am using packages such as rjson, jsonlite, RJSONIO, etc. I have tried different things as shown below but I got errors with all of them.

mydata <- fromJSON(paste(readLines("result_prod_14-15_08_17.json"), collapse=""))

The error I got is:

Error: lexical error: invalid char in json text.
                         {  "_id" : ObjectId("59920f495401ac79452a0
                 (right here) ------^

Using 'RJSONIO' package:

md <- stream_in(file("result_prod_14-15_08_17.json"))

produces the following error:

opening fileconnectionoldClass input connection.
Error: parse error: premature EOF
                                       {
                     (right here) ------^
closing fileconnectionoldClass input connection.

It must be something straightforward but since I am new to R I struggle to figure it out.