The building union has issued a national alert on a Chinese supplier following an asbestos scare at the construction site of the Queensland government's so-called "tower of power".

The CFMEU is also seeking an urgent meeting with Yuanda, which it claims has broken the law by exposing workers at 1 William Street, Brisbane, to asbestos-laden gasket material imported from China.

“This is a lethal product that has been proven to cause cancer,” CFMEU national secretary Michael O’Connor said.

“The use and importation of asbestos has been banned in this country since 2003 and the company has broken the law.”

Mr O’Connor said a CFMEU site delegate and safety representative unearthed the asbestos after he investigated the material in the course of his duties.

Asbestos removal signs could be seen at the construction site on Monday, and work on the tower has since resumed.

The state government has demanded a report into the incident at the privately owned development, which will house public service workers when complete.

Treasurer Curtis Pitt said it was premature to speculate whether it was definitely asbestos and what the incident meant for the sub-contractor.

“We’ve asked for a report from the builder to be reassured that all of the necessary steps have been taken to ensure safety on site for the workforce as well of course potential future tenants in government workers,” Mr Pitt said on Tuesday.

“We remain committed to becoming a tenant in that building – it’s something we’ve been signed up to by the previous government and something that we’d rather have more options on.”

The controversial 41-storey skyscraper, which will replace the tired George Street executive building, was initiated by the former Liberal National Party government.

Mr Pitt last year labelled the tower the “biggest financial debacle in Queensland’s history”.

Mr O’Connor said the union had been calling for action from the federal government on the importation of building materials to no avail.