City officials have issued a stop work order after some material fell from a crane in downtown Calgary on Wednesday.

It's not clear yet what led to the incident at the Eighth Avenue Place tower under construction on Wednesday afternoon. However, city officials say no further hoisting work will be allowed until inspectors can determine what happened and whether the public's safety can be guaranteed.

"We're at a point where we did identify that a piece of [iron] fell from a hoisting operation when the crane was lifting it," said Marco Civitarese, the city's chief building inspector. "Numerous pieces fell — some fell within the boundary of the project work and some fell outside the boundary of the project work, creating an unsafe condition to the public."

No one was injured and so far, no fines or charges have resulted.

Civitarese says the city has recently strengthened its safety regulations in light of a number of similar incidents in the downtown core.

Changes include higher fines and a requirement for buildings greater than five storeys to work with a daily forecaster to prevent wind-related incidents.