Maine regulators are scrutinizing a Spanish energy giant’s agreement to buy the parent company of Central Maine Power Co. as they consider whether to approve the $2.5 billion deal.

Iberdrola is seeking to purchase the remaining 18.4% of shares of Avangrid Inc., CMP’s parent. Avangrid, a publicly traded company, would become privately held, exempt from disclosing with the U.S. Securities and Exchange Commission detailed reports on transactions and its financial performance.

Iberdrola said in March when it announced the deal that it wants to increase its exposure to Avangrid’s network of electricity and gas utilities in the United States.

As a privately held company, Avangrid would have “greater operational flexibility and be relieved of the public reporting requirements under the U.S. federal securities laws,” the Connecticut-based utility said in a regulatory filing.

For example, Avangrid would not have had to file a July 8 disclosure of a subsidiary’s multimillion-dollar sale of a federal lease to Virginia Electric and Power Co.

Iberdrola’s desire for full ownership of Avangrid is in response to major changes in the industry, including volatile prices of commodities such as natural gas, greater regulatory oversight that has led to more uncertainty and a continuing need to raise capital to sustain growth, Avangrid said in a regulatory filing.

CMP asked the state Public Utilities Commission to waive a state law requiring a review of the deal.

In 2008, regulators authorized Iberdrola’s acquisition of 100% of the stock of Energy East, a predecessor of Avangrid, CMP said. As a result, Iberdrola indirectly owned 100% of the common shares of CMP and Maine Natural Gas through Iberdrola USA Inc., a wholly owned subsidiary that merged with UIL Holdings in 2015 to form Avangrid.

The deal will “not result in a change in control” of the electric utility and Maine Natural Gas, will “only modestly increase” Iberdrola’s ownership share of Avangrid, and will have no effect on customers, the utility told regulators.

Iberdrola’s move raises the issue of foreign ownership that figured prominently in last year’s unsuccessful campaign to replace CMP and Versant Power with a publicly owned and controlled utility. Critics say revenue and profit generated in Maine benefit the foreign owners of CMP and Versant, which is owned by Enmax, a Canadian energy company.

Our Power, an advocacy group that campaigned for the public utility, disputes CMP’s claims that tighter ownership by Iberdrola will change little, if anything. It says the Iberdrola-Avangrid deal will transfer ownership and control of the utility, directly influencing the accountability and transparency.

Treating Avangrid’s assets and business “as entirely its own involves a very fundamental change in the nature and extent of Iberdrola’s power over this public utility holding parent company,” it said.

Industry analyst John Quackenbush, president of JQ Resources, said foreign ownership of utilities is “fairly common.” Competition for investments is global and most utilities have between 10% and 15% foreign ownership and some are as high as 100%, he said.

The PUC allowed Our Power to be an intervenor in the case, citing its interest in “local control” and saying at least one member is a CMP ratepayer.

Intervenors receive official documents and may participate in PUC meetings. Mandatory intervention is granted to individuals or groups “substantially and directly” affected by regulatory proceedings and to government agencies, according to the PUC. For other groups, regulators decide who may intervene.

CMP objected to Our Power’s request to intervene. The group may seek “broad and intrusive” access to documents, not to help regulators consider CMP’s corporate ownership, “but rather to engage in a fishing expedition” to advance its political interests, CMP said.

CMP serves more than 636,000 electricity customers in southern and Central Maine. Maine Natural Gas has about 6,000 customers.

The PUC is expected to review information and testimony through mid-November.