Initially, the University of Otago research support facility building, in Great King St, was due to open in February.
However it was delayed because asbestos was discovered in the soil in 2017, putting the timeline for completion back to November.
University campus development division director David Perry said the asbestos-contaminated soil had now been removed, but the construction process had been slowed down by ''the need to break through boulders several metres below ground level''.
''Approximately 80% of the piling work has been completed, and this is expected to be finished in May,'' Mr Perry said.
He said it was unknown what effect the delay would have on the construction cost, which had an original budget of $49.8million.
The university was also still assessing what difference the rocks would make to the construction timeline, Mr Perry said.
The lab will be located beside the university's School of Physiotherapy building.
Contingency provisions had been worked into the original budget for the five-storey building, Mr Perry said.
In April last year, 70 people took part in a protest led by the New Zealand Anti-Vivisection Society against the university's planned use of the lab, and the group also protested in 2016, covering the wall of the construction site with more than 11,000 paper hearts.
Deputy vice-chancellor for research and enterprise Prof Richard Blaikie said last week the facility would meet stringent animal welfare regulations, as well as strict health and safety requirements.
It would feature the latest technologies, and underpin a wide range of university research, he said.
