The families of the victims and survivors of the Berkeley balcony collapse are being assured the case will be thoroughly investigated.

Alameda County District Attorney's Office announced yesterday it had opened a formal investigation into the balcony collapse last week.

Five Irish students and one Irish-American were killed when the balcony gave way, while seven others were left with serious injuries.

All the victims have now been laid to rest.

A team of investigators, prosecutors and victim witness advocates will be working on the case.

Speaking at a press conference, DA Nancy E. O'Malley said that multiple questions must be answered before a decision can be made on criminal liability.

"Once the investigation begins, I am limited in what type of information I can share with you", she said.

"We have got to make sure that whatever investigation we conduct and whatever findings we make, before the final decision is made, that we are doing so not in the court of public opinion - but rather something that can be evaluated and brought into the court of law", she added.

Assistant District Attorney, Teresa Drenick, told Newstalk Breakfast all options are open in the investigation.