BERKELEY (KRON) — A balcony that collapsed at a Berkeley apartment complex appeared too small to hold the 13 people, according to a structural engineer.

Engineer Grace Kang says California building codes during the past decade have required balconies to support 100-pounds per square foot. The previous codes called for 60 pounds of support per square foot.

Kang, who is also a spokeswoman for Pacific Earthquake Engineering Research Center at the University of California, Berkeley, says moving and dancing would have put additional strain on the balcony.

Six people, including five young Irish nationals, were killed and seven more hurt when a fifth-story balcony collapsed in Berkeley early Tuesday. City officials say they are investigating the cause of the collapse.

In a statement, Greystar Management, the property management company at Library Gardens, said it was working with officials to determine the cause of the accident and offered their condolences to the families of the victims.

“Our hearts go out to the families and friends of the deceased and those injured in this tragic accident,” the company said.

“As the property management company, we have taken precautionary steps to limit access to other balconies at the apartment complex as law enforcement completes its investigation. The safety of our residents is our highest priority and we will be working with an independent structural engineer and local authorities to determine the cause of the accident.”