Opposition parties and the leader of one of the province’s largest unions are calling on the Ontario Liberals to speak up about an OPP probe into alleged “irregular transactions” with outside vendors that involves provincial ministries.

NDP Leader Andrea Horwath said the Liberals’ silence on the issue is undermining confidence in the government. Progressive Conservative Leader Tim Hudak said Premier Dalton McGuinty or a senior official needs to step up and explain what’s going on.

Officers from the OPP’s anti-racket branch searched government offices at the Macdonald Block complex at Bay and Wellesley (pictured) last Thursday. The search warrants reportedly included the Ministry of Transportation and Ontario Realty Corp.

Investigators were there to look over transaction records of purchases of services and goods from private suppliers.

The probe apparently doesn’t include MPPs or political staff.

Ontario Public Service Employees Union (OPSEU) President Smokey Thomas is also urging the government to clear the air. None of his members are targeted in the investigation,  he said, but remain under a cloud of suspicion.

Two senior cabinet ministers have spoken out about the investigation. Finance Minister Dwight Duncan has said the only details he’s aware of are those he’s read in media reports. He hasn’t received a police briefing.

And Environment Minister John Gerretsen said his department isn’t involved in the investigation.

No government official has clarified which ministries are under investigation.