Hudson River helicopter crash cause not yet known, NTSB says

NTSB Chairman Jennifer Homendy said the agency will not speculate on cause. 

"We do not have a preliminary cause. That takes time," Homendy said. "We will not speculate on cause ever, but we will not be determining any sort of preliminary or probable cause at the scene of an accident. We don't do that."

https://www.cbsnews.com/newyork/news/helicopter-crash-hudson-river-ntsb/