On Tuesday, Federal prosecutors said that an ex-medical technician has been convicted of interfering with narcotics at a Colorado hospital, due to which authorities have requested about 3,000 people who underwent surgery there to get tested for blood-borne diseases.

The US Attorney John Walsh said in a statement that the case has been brought after the defendant was found swapping a syringe that has fentanyl citrate, a strong synthetic opiate, for a dose of an unnamed substance during the surgery of a patient recently.

Walsh said that the shocking incident has taken place at the Swedish Medical Center in suburban Denver, and the hospital has immediately fired the surgical technician being questioned in the case Rocky Allen, notifying law enforcement.

Later on, a federal grand jury indicted Allen on one count of tampering with a consumer product and one count of taking a controlled substance by cheating, both of which are felonies.

In withdrawing his license, a state regulatory board has discovered Allen tested positive for marijuana and fentanyl in his system post incident.

The conclusion has resulted into concerns that he could have been an intravenous drug user in a position of directing injections to patients with needles used by him, though no patients were known to have got injured at the time of surgery by his actions.

However, hospital officials have precautionary started notifying 2,900 patients who had surgery at the facility between August 2015 and previous month, advising them to undergo free screenings for HIV and hepatitis B and C.

A hospital spokeswoman said that as of Tuesday, over 75% of the patients had been contacted and most of them have got tested.