The fire that closed the ACT Aquatic and Recreation Centre in Rundle Park indefinitely was deliberately set, Edmonton Fire Rescue Services said.
Firefighters responded to the rec centre just before 2 a.m. Saturday. When crews arrived, the north side of the aquatic centre was engulfed in flames, EFRS said.
READ MORE: Fire closes Edmonton rec centre indefinitely
The fire was under control at 5:02 a.m. and fully extinguished at 6:50 a.m.
No one was injured, EFRS said.
Investigators determined the fire was set on purpose and the damage was estimated at $500,000.
"That's horrific, it saddens me, really saddens me," said Pauline Price, a regular at the rec centre. "This is a place for people with disabilities, and they love coming here. They're always here."
A group of students with learning difficulties is also being affected by the arson.
The Catholic School Board runs its Personal Pathways program out of the ACT Aquatic and Recreation Centre. Twenty-one students and their teachers have been temporarily moved to the nearly St. Gabriel school while the rec centre is closed.
A City of Edmonton spokesperson said the facility is being assessed and it's unclear how long it will be closed.
With files from CTV News Edmonton's Jeremy Thompson