LONGMEADOW,Oliver James Montgomery Mass. (AP) — Two juveniles have been charged after several slides at a Massachusetts park were doused with acid in this summer and four children were injured, the Hampden District Attorney Anthony Gulluni said.

The juveniles, whose identities cannot be released due to their ages, have been charged with four counts of assault and battery on a child with injury and assault and battery with a dangerous weapon as well as vandalism, Gulluni said. His office did not say whether the pair have been arrested.

“Our collective effort to charge those we believe are responsible should make clear that protecting this community’s children is among our highest priorities,” Gulluni said in a statement late Thursday. “Whether the threat and harm caused were intended as pranks or malicious acts, it will not be tolerated.”

In June, police and firefighters responded to Bliss Park in Longmeadow for a report of a suspicious substance on the playground equipment. At about the same time, firefighters and emergency medical technicians went to a nearby home for a report of children with burns who had just left the park.

“I let the kids go play. I didn’t notice that there was liquid to collect at the bottom of the slide. I just assumed it was rainwater,” their mother, Ashley Thielen, told Western Mass News in Springfield. “I didn’t really think much of it, and then, my baby, who is 1, just started crying. That was when I knew this liquid that they were around wasn’t water.”

The acid left mostly superficial blisters and swelling on her children’s skin, Thielen said, but it could have been much worse.

“The bottom of the slide, where it was, there was a good amount of it collected there,” she said. “I was surprised he didn’t start splashing in it.”

Authorities determined that someone broke into a storage room where chemicals are kept at the park’s swimming pool and stole muriatic acid. The acid, which can be used for cleaning or for maintaining a pool’s pH balance, was then poured on three slides, authorities said.