PROVIDENCE, R.I. — Several Democratic members of Congress are asking the head of the U.S. Environmental Protection Agency whether three agency scientists were prevented from speaking at a conference because it included a discussion of climate change.

In a letter to EPA Administrator Scott Pruitt released Tuesday by the office of Sen. Sheldon Whitehouse, members of the Rhode Island and Massachusetts delegations ask why the scientists were prevented from speaking at last week’s conference on the health of Narragansett Bay.

They also asked who made the decision and how it was made. They also asked for all communications related to the decision.

The EPA did not explain the decision but said it was not an agency conference.

The letter also requests EPA’s policy on scientists’ participation in conferences.