Massachusetts will join California and New York in investigating claims that Exxon Mobil knew about the effects of climate change due to the burning of fossil fuels and hid the information for decades.

In a press conference Tuesday, Massachusetts Attorney General Maura Healey said her state would investigate the claims as well. New York Attorney General Eric Schneiderman has announced he is investigating what Exxon Mobil knew and when, and reports indicate California Attorney General Kamala Harris began doing the same in January.