HARRISBURG — Lawmakers briefed on Gov. Tom Corbett’s package of financial incentives for a planned petrochemical refinery in Western Pennsylvania said Friday that it could also include the cost to clean up pollution from the zinc smelter that has operated there for decades.

The revelation by two state senators is the latest about Corbett’s negotiations on the facility with Shell Oil, a subsidiary of Netherlands-based oil and gas giant Royal Dutch Shell PLC.

The Republican governor’s administration has shared with the public sparingly those plans on what lawmakers say would be the biggest package of taxpayer-paid incentives in Pennsylvania’s history for a project being billed as the reindustrialization of the state.

Two senators briefed on the project, Sen. John Blake, D-Lackawanna, and Sen. John Wozniak, D-Cambria, said the project deserves serious consideration. Blake cautioned that the Corbett administration must show that the cost of the incentives must match the potential economic benefit to the state.

The projected multibillion-dollar ethane cracking plant would convert ethane from the area’s bountiful Marcellus Shale natural gas liquids into more profitable chemicals such as ethylene.

Blake said the administration’s financial incentive plans for Shell revolve around a recently disclosed tax credit worth up to $1.65 billion over 25 years and a newly created tax-free zone for the site that the Legislature approved in February.

Department of Community and Economic Development Secretary Alan Walker and the other administration officials who briefed Blake and Wozniak on Wednesday could not immediately provide a figure on the value of the newly created tax-free zone site to Shell, the senators said.

The tax-free zone “is a very lucrative tool, and I don’t think we could have lured Shell without it,” said Blake, who briefly served as the department’s secretary under former Gov. Ed Rendell.

But because Shell likely would have no state tax liability, it could sell up to $66 million in tax credits a year to companies that use its feedstock as a way to encourage a local market in Pennsylvania, senators said.