Sunderland fans say they had bottles, coins and even flares thrown at them by rival fans at this weekend's game against Coventry City.
The two sides faced each other yesterday at the Stadium of Light in a match which saw the away team win 5-4.
Following the match on social media Black Cats supporters have said they saw a number of items being thrown at them from the away supporters' section of the ground, which is the upper area of the North Stand.
One fan has posted a picture of someone with a cut to their head.
Independent fan group The Red and White Army has also said it aware of complains from fans about what happened.
SAFC chairman Stewart Donald said on Twitter he is "distraught" at what SAFC supporters appeared to be subjected to.
In response to a query from a fan on Twitter about the situation he replied: "I heard it and saw.
"I have requested a full report sent to me ASAP.
"I am distraught our fans appeared to be subjected to what I think I saw and if so is completely unacceptable.
"I should have gone over in person myself to help stop it.
"I will say more once I have investigated."
On the Ready To Go message board, one poster wrote: "They were disgusting, flares, bottles, coins and even the odd sarnie."
Another wrote: "A bottle hit a fella near us.
"He looked really shaken up as it was half full and it hit him square on.
"Very lucky not to have been seriously injured."
Another wrote: "A pyro hit a bloke in his 60s next to me.
"Had grey hair but it was dyed blue.
"Hope anyone who was hit is OK."
One posted: "Worst I've ever seen today.
"All sorts getting thrown down everytime they scored."
Independent fan group The Red and White Army has since tweeted: "Having received many reports from our members about missiles being thrown by Coventry fans into the North Stand, we'll be talking to the club about safety issues.
"We'll report back any updates from the club."