Families of the CTV victims have been disheartened by delays in the police investigation into the building's collapse.

Police had hoped to decide by the end of the year whether the collapse, which killed 115 people, was a case of criminal liability, but it's taken longer than expected to arrange a reconstruction of the building, to test critical elements of the structure.

More than 100 witnesses have been interviewed, and search warrants executed as part of the investigation.

Maan Alkaisi, who lost his wife in the collapse, says engineers are to blame for the building's failure, and now other engineers are preventing the families getting justice.

"This was the biggest engineering failure in the country. They should do the job properly in a way that reflects the importance of what happened there," he said.

"I mean, it's five years, not like five months. After years we still have to wait more."