Police are investigating a fire that burned the wetlands Saturday night at Lippold Park after an unknown person set off fireworks, officials say.

The blaze began between 9:30 and 10 p.m. Saturday, Crystal Lake Park District Executive Director Jason Herbster said.

“Luckily we had an officer out there at the time that it happened,” Herbster said. “A resident called it in right away.”

The Crystal Lake Fire Department also responded to the fire, which remains under investigation.

“We don’t know who did it,” Herbster said. “We had one person call yesterday with some information, but it’s still being followed up.”

Crystal Lake resident Jason Solarz was in his backyard when he heard fireworks go off and noticed a fire shortly after, he said.

“There were a few large fireworks that went off in the area, the last one looked kind of low,” Solarz said. “Shortly after, a small area was on fire, and it quickly spread. The fire department got there quickly and hit it from both sides to contain the spread and then they were able to get it out completely.”

The fire damaged only the wetlands, which were “probably as dry as they’ve been in seven years,” Herbster said.

Because the blaze was contained to one area, Lippold Park remained open Saturday.