A director of Glenavon Football Club has said it may be forced to close if attacks on its ground continue.
It is thought that a window at the club bar was prised open
George Malone was speaking after the fire at Mourneview Park, home of the Irish League club in Lurgan.
Seven fire crews battled to bring the blaze, which broke out at about 0630 BST on Monday, under control.
A supporters' club bar under one of the stands was destroyed. The fire brigade found the remains of a petrol bomb device.
It is thought that a window at the supporters' club bar was prised open and a petrol bomb was thrown inside.
Mr Malone said he feared for the future of the club, if the constant vandalism continued.
Club officials assessed the damage caused to the bar
"We have tried everything we can to curtail this but it seems to be an impossibility," he said.
"The police are doing all they can to keep these guys out.
"All the windows are broken, the far stand is damaged, seats are damaged on a regular basis.
"If this keeps going on, this club will not be able to continue, the way things are going."
History of attacks
It is understood the damage is mostly at the members' end.
As well as the bar which was gutted in the blaze, two other bars and the press box were smoke and water damaged.
The damage is estimated at between £30,000 and £40,000. A motive for the attack has not been established.
Forensic experts are examining the remains of the petrol bomb.
Divisional Officer Walter Johnston said it was a serious fire.
The Lurgan football ground has been attacked by arsonists on a number of occasions.
On Tuesday, the scheduled first leg of the promotion/relegation play-off between Glenavon and Crusaders will go ahead at Mourneview Park as planned.