One in seven employees of companies contracted to work on Ireland's railways failed a drug test in the last year.
According to the Irish Times the tests were carried out before any work started.
Irish Rail says it is looking at a number of options to combat the problem, which could include mandatory testing.
Company spokesperson, Barry Kenny, said: "Well we conducted random drug and alcohol testing on contracted personnel and employees, but we woukd be concnerned about the high rate of failure amongst contractors.
"So we are looking at strengthening this further, already if a contractor fails a drug test we will not allow the individual to work on our network."