The State Department has preserved information on Ukrainian children abducted by the Russian government during its war in Ukraine that lawmakers feared had been deleted, Secretary of State Marco Rubio said Thursday night.

Researchers at Yale University, who were tracking tens of thousands of abducted Ukrainian children, had created a database as one project under the Biden administration State Department’s Conflict Observatory program. In addition to tracking potential war crimes committed by Russia in Ukraine, the Conflict Observatory tracked the civil war in Sudan. Lawmakers feared that the database on the Ukrainian children had been deleted when the State Department cut funding for the group tracking the abductions.

“The data is secure,” Mr. Rubio told reporters on his plane flying from Suriname to Miami at the end of a three-nation tour of the Caribbean and South America. He said the database would be transferred to “the appropriate party,” without specifying who, and that the program would no longer operate because the funding had been cut as part of a halt to almost all foreign aid when President Trump took office in January. The data is likely to be transferred to the International Criminal Court and Europol, Europe’s main law enforcement agency.

The Yale School of Public Health Humanitarian Research Lab, which was tracking the abductions, had counted more than 30,000 children taken from Ukraine to places including Russia and Belarus since Russia’s full-scale invasion of Ukraine began in 2022. When the funding ended in January, the lab had put information into the database on thousands of children, including detailed dossiers on more than 300 of them, traced to Russia’s coercive adoption system.

Ukrainian officials say Russia has abducted 20,000 children from the country.

In 2023, the International Criminal Court issued an arrest warrant for President Vladimir V. Putin of Russia and an aide, accusing them of war crimes over the abduction and deportation of Ukrainian children. The Kremlin has denied accusations of war crimes but has not been secretive about the transfers of Ukrainian children to Russia.

The Yale lab had intended to hand the database over to Europol and the International Criminal Court. In addition to the arrest warrant for Mr. Putin over the deportations, the court also issued one for an aide, Maria Lvova-Belova. The purpose of the database is to help the court bring charges against more Russian officials.

This month, U.S. lawmakers sent a letter to Mr. Rubio asking about the status of the project and saying they had heard the database might have been deleted after the funding was stopped.

Now with the effort to preserve the final stages of data collection, the project the Yale lab was leading is supposed to remain operational for six weeks to give experts time to transfer the database.

The main contractor for the program was the MITRE Corporation, a nonprofit that often does work for U.S. intelligence agencies. The Yale lab was a subcontractor under MITRE. Congress had allocated funding for the project from 2022 to this year.

After lawmakers expressed worries about the database, MITRE said in a statement that it had not been deleted and was in the hands of another specialist group.