SAN DIEGO — A towering Eucalyptus tree fell Thursday morning during a family event at the Marine Corps Recruit Depot in San Diego, injuring 15 people, most of whom suffered scrapes and bruises.

Two people — an 8-year-old girl and a 77-year-old woman — were taken to a nearby hospital for observation, Maj. Neil Ruggiero said.

There were no broken bones and no Marines were injured.

The tree toppled at about 9 a.m. Thursday as a drill sergeant was talking to the group on a lawn. Most of those attending were family members of Marines who will graduate Friday from boot camp. The families had just gathered to watch the recruits pass during a motivational run, Ruggiero said.

It was unclear what caused the tree to fall. There was no wind at the time, but it's possible an earlier rain had loosened the tree's shallow roots, Ruggiero said.