They are worried that the two men, who were stabbed on Sunday night near the stage of the Primal Scream concert on Glasgow Green, on the east side of the city, may not be aware of the attack.
A third victim, a 27-year-old man from Lanarkshire, who was also stabbed, witnessed the assault on the other two. He was treated at Glasgow Royal Infirmary and vaccinated against Hepatitis B.
Strathclyde Police and Greater Glasgow Health Board have advised any of the 7,200 fans who attended the concert, and who suspect they may have been "jagged" or show signs of pin-prick punctures on their skins, to go to their nearest hospital for a check-up as a precaution against possible infection.
The 27-year-old man, who did not want to be named, was standing near to the front of the stage at around 10.45pm when he noticed a man brandishing the syringe.
He saw the attacker plunge the needle into the shoulder of a man in front of him and then strike another man on the upper arm.
He grabbed the assailant's arm but during the course of the struggle felt the needle going into his own arm.
A police spokeswoman said: "Because of the crushed conditions at the time, the 27-year-old man is unsure whether the two other men were or are aware that they had been assaulted."
The Edinburgh-based concert promoters Regular Music say that around 70 per cent of the 6,300 tickets sold were bought in the west of Scotland area, although around 7,200 people attended the gig by the hugely popular rock band.Reuse content