The MACC today confirmed that it opened six investigation papers on the Penang undersea tunnel.

"The first investigation paper was opened on July 2017, while five others were opened on Jan 2018.

"Five of the investigation papers have been completed and referred to the deputy public prosecutor, and three were returned to the commission for further investigation.

"Two more are still being studied by the deputy public prosecutor, and the remaining ones are still being investigated by the MACC," the statement read.

The contentious RM6.3 billion project was again in the headlines after blogger Raja Petra Kamurudin published purportedly leaked MACC investigation papers on his blog.

Five DAP leaders were implicated in these documents, including Finance Minister Lim Guan Eng and Penang chief minister Chow Kon Yeow, for allegedly receiving kickbacks from project contractor Consortium Zenith Construction Sdn Bhd (CZC).

Lim branded Raja Petra's allegations "ridiculous lies," while CZC senior executive Zarul Ahmad Zulkifli dubbed them "pure fiction."

Both said the claims were meant to tarnish their reputations, and that of the Penang and federal governments.

Lim said yesterday that the contract for the tunnel project was awarded to CZC via an open tender system, and vehemently denied that corruption has been involved.

Today, Zarul pointed out that he had been remanded for 11 days to assist MACC investigations into the project when BN still held federal power prior to last year's general election.

He added that the commission had even hired external consultants to see if the CZC was fair in its pricing.

The allegations had prompted Prime Minister Dr Mahathir Mohamed to accuse Raja Petra of being a "liar," while the MACC lodged a police report over his blog post a day later.

Part of the Penang Transport Master Plan (PTMP), the undersea tunnel is a 7.2km tunnel that connects George Town on Penang Island to Butterworth on the mainland.

The project also encompasses two roads connecting Gurney Drive and Air Itam to the Tun Dr Lim Chong Eu Expressway, and another paired road connecting Tanjung Bungah to Teluk Bahang.