A crane brought in for earthquake-related repairs at the Washington National Cathedral toppled over Wednesday, injuring its operator and damaging buildings days before the cathedral was to welcome thousands of visitors, including President Obama, for events commemorating the 10th anniversary of Sept. 11.

The cathedral was not damaged in the accident. It has been closed for repairs since the Aug. 23 earthquake, and Friday’s planned reopening is part of a three-day commemoration scheduled to include a prayer vigil and memorial concerts for 9/11 victims and troops killed in Iraq and Afghanistan. Obama is slated to speak at a Sunday night concert.

Cathedral officials would not say whether the accident affects their plans to reopen the cathedral Friday.

The operator of the crane, which has a 500-ton lifting capacity, was using it to hoist supplies up to the cathedral’s central tower, which suffered cracked spires and statues during the earthquake. The operator was lowering the boom when the crane tipped over shortly before 11 a.m., fire department Battalion Chief John Donnelly said.

The operator was inside the crane’s cab when it fell, and was treated for non-life-threatening injuries, Donnelly said. Twenty people were inside nearby buildings that were damaged in the accident, but none was hurt, he said.

Heavy rains and wind gusts of 40 to 50 mph were reported in the area at the time of the accident, but, “We don’t know why it collapsed,” Donnelly said.

Labor Department spokeswoman Leni Fortson identified Crane Service of Upper Marlboro as the operator of the crane and said the accident was under investigation.

When asked whether the accident scene could be cleared by the time of Obama’s scheduled arrival Sunday, Donnelly said, “It’s gonna be tight.”

According to OSHA inspection records, Crane Service was cited in 2007 and paid a $450 fine for having a worker within the swing radius of a crane, which is a work hazard. Crane Service officials did not return requests for comment by Wednesday evening.

The Crane Service Web site includes photographs of a tall yellow crane at use on the cathedral grounds and notes the company’s projects at other area locations including the Capitol Visitor Center and Jefferson Memorial.

The crane lay broken and twisted on South Road, which runs along the cathedral’s south side. The road, mostly used by employees, passes by the main office of the Episcopal Diocese of Washington, also known as Church House. The tip of the crane lay in front of Church House.

The Rev. Simon Bautista, canon for Latino Ministries for the diocese, said he was on a conference call with his staff planning an Oct. 8 Latino celebration when the accident happened. The window of his second-floor Church House office overlooks the parking lot.

He said he heard a sound like “thunder” and, “My office started shaking.”

He said it was miraculous that no one had been killed or seriously injured.

“You can see that this was a divine hand that kept something else from happening,” Bautista said.

The building that sustained the most damage was Herb Cottage, which is next to Church House on the east side. Its roof was clipped by the falling crane, Donnelly said. The building, one of the oldest on the grounds, has been closed to the public since the earthquake.

The National Cathedral School and St. Albans School, both in their first day of classes, suspended coordinated classes in which students cross the cathedral grounds to study at each others’ school. There was no evacuation and no one was injured, spokesmen for the schools said.

Post staffer David Nakamura contributed to this report.