Police have launched an investigation after flares were let off outside Ipswich Town's Playford Road training ground on Monday.
Officers were called to reports of people letting off flares in Playford Road on Monday morning.
On arrival, police found that the group had left the scene in the direction of Rushmere Heath.
Training for Tuesday night's match against Northampton Town was reportedly suspended for 10 minutes after a sign on the fenced-off perimeter caught fire.
Ipswich Town independent supporters' group 'Blue Action' later posted footage online of a protest outside the training ground.
A spokesman for Suffolk Constabulary said: "Police were called at 10.30am on Monday, February 15, to reports of a number of people setting off flares on Playford Road, in Ipswich.
"Those involved reportedly left the scene on foot, heading towards Rushmere Heath.
"Police attended and searched the area but found no trace of any suspects. Enquiries are ongoing.
"Anyone with any information about this incident, or who saw anything at the time, is asked to contact the police, quoting incident number 88 of Monday, February 15."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here