Effort to identify bodies will take weeks or months , head of forensics team says . Rebel leader says Ukraine military breaks through to part of crash site . Comment: Washington preparing further sanctions against Moscow .
Effort to identify bodies will take weeks or months , head of forensics team says . Rebel leader says Ukraine military breaks through to part of crash site . Flare-up in fighting near crash site in eastern Ukraine turns back investigation team . Washington preparing further sanctions against Moscow .