Melted plastic sagged from a large plastic tunnel and a stench hung in the air at the Lyndale Community School playground, where about half the play area was roped off with yellow caution tape Monday.
The playground was set on fire Sunday, the fifth time a public school playground in Minneapolis has been targeted by arson since mid-June.
The string of fires has frustrated parents, puzzled district officials and stymied authorities.
No one has been arrested. Neither police nor fire officials will say the fires are connected.
"Who could have done that? It's unbelievable," parent Tenzin Nyima said after one of his two children attending Lyndale pointed out the damage Monday. "Schools don't have money to spend on stuff that's destroyed," added Carrie Swanson, who has four students at the school.
The blaze created heavy smoke and fire about 2 p.m. Sunday outside the school, at 312 W. 34th St., before being quickly extinguished, authorities said. Police say they are treating the fire as an arson.
All of the targeted playgrounds remain unusable, said district spokeswoman Larissa Chinwah, who said total damage has swelled to about $220,000.
It was the second case of an intentional fire at Lyndale; a slide was torched four years ago, according to parents.