Materials seized last year when former President Barack Obama ordered two Russian compounds in the U.S. closed included destroyed materials that could have aided the probe into claims Russia meddled in last year's presidential election, The Hill reported Saturday.

The materials included antennas, electronics, computers, file cabinets and other items and points to the possibility Russians were conducting intelligence in the U.S., which would be illegal. Officials suspected the Russian operation included the potential of hacking U.S. voting machines.

Obama closed the compounds in Maryland and New York as part of the administration's retributions for intelligence that indicted Russia was tampering with the 2016 presidential election. At least 35 diplomats were expelled.

At the time, White House officials said the move was due to harassment of U.S. personnel in Russia, CBS News reported Friday. President Donald Trump is reportedly considering returning the compounds, used as retreats, to Russian control, a move opposed by many senators including South Carolina Republican Sen. Lindsey Graham.

"These properties were seized because 17 U.S. intelligence agencies confirmed that Russia used covert cyberattacks, espionage, and harmful propaganda to try and undermine our democracy, in addition to the fact that U.S. diplomats in Russia faced repeated harassment from Russian security services," the senators wrote.

Senators voted last week 98-2 approving a bill that would impose additional sanctions against Russia for its actions involving U.S. elections and included a provision that would require congressional approval to return the compounds to Russia, CBS reported.