Quebec provincial police are conducting a series of raids across Quebec, including at the headquarters of the province's largest labour federation.

The raids Tuesday are part of an investigation into alleged money laundering in the construction industry.

'We have nothing to hide.'— Michel Arsenault, QFL president

Police are executing search warrants at the Montreal offices of the Quebec Federation of Labour (Fédération des travailleurs et travailleuses du Québec) in addition to homes and businesses in Laval, Repentigny, Le Gardeur and Boisbriand.

The QFL is Quebec's largest union federation, representing more than 500,000 members and about 40 unions from across North America.

At a news conference Tuesday afternoon, QFL president Michel Arsenault said police wanted to see all paperwork the federation had on construction industry employers dating back to 2006.

"They were looking for some construction companies who, according to them, weren't paying their taxes," said Arsenault.

He said police left with a pile of documents measuring about 10 centimetres thick.

"We have nothing to hide," he told reporters.

Arsenault said police assured him that the lucrative QFL Solidarity Fund, a venture capital firm with more than $6 billion in assets, was not under investigation.

"The solidarity fund is solid," said Arsenault.