A child is in critical condition after part of a tree fell on a group at the San Antonio Zoo Wednesday afternoon.

The incident happened around noon, local media reports say. Six others were injured and taken to a hospital to be checked out. 

"We hear what sound sounded like fireworks, a crackling noise," Chris Ryan told FOX 29. "I turn around and realize that the branch was falling down - and that crackling noise was the breaking of wood!" 

The zoo's security and emergency medical technicians quickly responded and treated the injured guests. San Antonio police and fire crews were at the scene within minutes. 

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"It was a freak accident. It was so scary," witness Brandy Lorraine told the TV station. "I saw a woman running for help with blood on her hands. I heard people screaming. I just hope everyone is OK. Thinking about it now is even scarier because any little detour could have put us in that spot."

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"We are working with our internal and external teams to investigate the cause of the breakage to prevent this unusual event from happening again," Tim Morrow, president and CEO of San Antonio Zoo tweeted Thursday morning. 

A large part of a cedar elm tree "unexpectedly broke and fell" on the guests, zoo vice president of marketing Hope Roth told mysa.com. The incident was referred to as an "unfortunate accident."

The zoo will reportedly be open Thursday.