Police are appealing for witnesses after a bottle was thrown onto the pitch during Sunday's Old Firm match at Ibrox.
It's understood that during half-time, between 12.45pm and 1pm, a glass bottle was launched from the Copland Road Stand onto the pitch. Broken glass was found scattered in front of the goalposts.
The second half was delayed after Joe Hart had to point out shards of broken glass laying in his penalty area.
Police Scotland said the missile could have left someone seriously injured and are calling on anyone with information to come forward.
Inspector Brian Fraser, of Greater Glasgow’s Divisional Violence Reduction Unit, said: “Luckily no-one was hurt as a result of this incident, however, it could have caused serious injury.
“I am appealing to anyone who witnessed the bottle being thrown or who has any information about the incident to please get in touch.
“Anyone with any information which could assist our investigation should call police via 101, quoting incident 0892 of 3 April.”
In a separate incident, a member of the Celtic staff was hit with another bottle and required stitches for a head injury.
A Celtic spokesperson said on Sunday: "We can confirm that a member of our backroom staff was struck by a glass bottle.
"He required urgent medical treatment and stitches to a head wound. The matter is now in the hands of Police Scotland."
A Rangers spokesperson previously told Sky Sports News: "We are assisting Police Scotland regarding both incidents and can confirm that stadium CCTV is being reviewed.
"We strongly condemn both incidents and the perpetrators will be banned."
