The residential component of the $550 million Nishi complex in Acton and the Astin project on Northbourne Avenue in Braddon both look set to sit idle for days if not weeks after the collapse of builder Ply Ltd on Monday afternoon.

Administrators say it might be a week before a return-to-work date can be given to more than 100 construction workers locked out of the two sites. The collapse affects many hundreds more Canberra building workers who are employed by subcontractors owed millions of dollars by Ply.

But the director of developer Molonglo Group took to breakfast radio on Wednesday to reassure investors the troubled Nishi complex would be finished, but warned it may be delayed by a few weeks.

There will be complex negotiations during the next several days between developers, Ply, subcontractors, the liquidators and the building unions to establish what is owed and how much money is available to pay creditors.

Sydney-based liquidator Alan Hayes, of Hayes Advisory, said on Tuesday he anticipated seven days before a date could be set for a return to work.

"Our meetings with the two principal developers have been pleasing," Mr Hayes said on Tuesday.

"Our aim is to facilitate a return to work on those major sites but to do that we will require co-operation from all the major stakeholders.

"It's too early to speculate about when they'll be back on site but we're hopeful of being able to disclose some positive news within a week."

More than 230 apartments are under construction at Nishi while Astin will have 145 units.

Nishi developers Molonglo Group said on Tuesday it was "shocked" by the collapse of the main contractor on the project but the developer said it has paid all its bills to Ply, which called in the administrators on Monday evening.

A spokesman for Molonglo subsidiary Nishi Residential Building Ltd said in a statement on Tuesday it was "confident" that the massive building job would be finished on time.

The project has been dogged with safety problems over the past several months causing delays and improvement notices by work safety

authorities. Many Nishi apartments have been sold off the plan and investors face a nervous wait for news of their purchases.

Molonglo's statement contained no concrete assurance of an on-schedule completion.

"Nishi Residential Building Ltd, the developer of the NewActon Nishi apartments, has been shocked by the construction company, Ply (ACT) Pty Ltd placing itself into administration yesterday afternoon," the statement said.

"All obligations and payments due from Nishi Residential Building Pty Ltd to Ply (ACT) Pty Ltd have been paid and are completely up to date as of yesterday.

"The current situation that has arisen is a matter between Ply (ACT) Pty Ltd and the administrators.

"We are confident in working with the administrator, and that the Nishi apartments will be completed on time."

Ply Director David Murphy has pledged to work with the administrators to try to minimise the disruption caused by the company's collapse.