New York (CNN Business) The long-time effort by Sprint and T-Mobile to merge has hit another roadblock.

New York and California's state attorneys general filed a lawsuit seeking to block the proposed merger Tuesday, along with seven other states and the District of Columbia. The lawsuit was announced by New York Attorney General Letitia James and California Attorney General Xavier Becerra.

"When it comes to corporate power, bigger isn't always better," said Attorney General Letitia James.

Sprint S T-Mobile TMUS Both companies' stocks fell on the news of the lawsuit. Shares ofdropped more than 6%, whilefell 2%. The companies did not respond to CNN Business' request for comment.

BREAKING: We're leading a coalition to block the proposed merger of T-Mobile & Sprint.



The merger would deprive customers of the benefits of competition & drive up prices for cellphone services.



When it comes to corporate power, bigger isn't always better. #Megablock — NY AG James (@NewYorkStateAG) June 11, 2019

Along with New York and California, attorneys general from Colorado, Maryland, Michigan, Mississippi, Connecticut, Virginia, Wisconsin and the District of Columbia have signed onto the lawsuit alleging that the merger would drive up prices for cell phone services. James said at a press conference Tuesday that the suit is the culmination of a yearlong investigation.

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