HARRISBURG (AP) — Gov. Tom Wolf on Friday followed through on his threat to veto a bill to provide potentially hundreds of millions of dollars in tax breaks for petrochemical plants that use natural gas extracted in the state.

In his veto message, Wolf said he could support awarding an incentive like the one in the bill, but only after a thorough analysis of a proposed project.

While the bill made concessions to labor unions, saying that eligible projects had to pay prevailing wage rates, Wolf said the bill was missing any sort of mechanism to investigate and enforce the provision.

The Republican-penned bill was never the subject of a hearing, and Wolf’s office has said lawmakers passed it without negotiating it with the governor.

It passed both Republican-controlled legislative chambers by veto-proof majorities in early February.

It authorized the “energy and fertilizer manufacturing tax credit” for projects that required at least $450 million in construction and start-up costs and that create at least 800 jobs. Wolf’s administration estimated the tax credit would be worth about $22 million annually per plant and expire at the end of 2050.

A similar 2012 state law that provides a tax credit for refining ethane into ethylene helped lure Shell’s multi-billion-dollar refinery, now under construction in Monaca, in Beaver County.