PORTLAND, Maine (AP) — A walkway collapse that injured 11 people at an open lighthouse event in Maine was caused by rotted support beams, police said Tuesday.

The collapse at Doubling Point Lighthouse in Arrowsic on Saturday sent five of the 11 hurt to the hospital with injuries that were not life-threatening. The visitors were participating in Maine Open Lighthouse Day, in which beacons all over the state are open to the public for tours.

There are no plans for a criminal investigation into the collapse, said Chief Deputy Brett Strout of the Sagadahoc County Sheriff’s Office. The lighthouse is closed to the public for an indefinite amount of time, and it’s unclear when it could be reopened or the walkway will be rebuilt.

The collapse of the walkway led to a chaotic scene in which visitors fell tumbling to a mudflat several feet below. Multiple public safety departments from around the area responded.

“Folks got down there as quickly as they could and tended to the injured. That’s what we all want,” Strout said.

Friends of Doubling Point Light, a nonprofit group, serves as the steward of the lighthouse, which was built in the late 19th century and is an active aid to navigation. The nonprofit group is working with local authorities in the aftermath of the accident, said Karen McLean, a member of the group.

McLean declined to comment further. The group took over stewardship of the lighthouse, located in a small town 40 miles north of Portland on the Kennebec River, in 1998.

The U.S. Coast Guard relies on the lighthouse as an aid to navigation, and it’s located not far from Bath Iron Works, a major shipyard on the Kennebec.

The damage to the walkway did not affect the lighthouse’s functionality as a navigation aid, and the Coast Guard is not involved in the response to the collapse, said Petty Officer Lyric Jackson. The Coast Guard’s responsibility is “to change the lightbulb,” Jackson said.