SAN JUAN, Puerto Rico — Puerto Rico’s governor announced that the U.S. territory overwhelmingly chose statehood Sunday in a nonbinding referendum held amid a deep economic crisis that has sparked an exodus of islanders to the U.S. mainland.

Nearly half a million votes were cast for statehood, about 7,600 for free association/independence and nearly 6,700 for the current territorial status, according to preliminary results. Voter turnout was just 23 percent, leading opponents to question the validity of a vote that several political parties had urged their supporters to boycott.

And the U.S. Congress has final say in any changes to Puerto Rico’s political status.

But that didn’t stop Gov. Pedro Rossello from vowing to push ahead with his administration’s quest to make the island the 51st U.S. state and declaring that “Puerto Rico voted for statehood.” He said he would create a commission to ensure that Congress validate the referendum’s results.

“In any democracy, the expressed will of the majority that participates in the electoral processes always prevails,” Rossello said. “It would be highly contradictory for Washington to demand democracy in other parts of the world, and not respond to the legitimate right to self-determination that was exercised today in the American territory of Puerto Rico.”

It was the lowest level of participation in any election in Puerto Rico since 1967, according to Carlos Vargas Ramos, an associate with the Center for Puerto Rican Studies at Hunter College in New York. He also said that even among voters who supported statehood, turnout was lower this year compared with the last referendum in 2012.

“Supporters of statehood did not seem enthusiastic about this plebiscite as they were five years ago,” he said.

Puerto Rico’s main opposition party rejected the pro-statehood result.

“The scant participation … sends a clear message,” said Anibal Jose Torres, a party member. “The people rejected it by boycotting an inconsequential event.”

The referendum coincides with the 100th anniversary of the United States granting U.S. citizenship to Puerto Ricans, though they cannot vote in presidential elections and have only one congressional representative with limited voting powers.