WASHINGTON -- When U.S. officials entered shuttered Russian compounds in Maryland and New York last December, they found damaged materials that could have been used in intelligence gathering and that former officials say could have been useful in the ongoing investigation into Russian interference in the 2016 election.

The compounds, which had been used for decades as retreats for Russian diplomats, were shut down by the Obama administration as part of a package of punitive measures in response to Russia's meddling in the election. The White House expelled 35 diplomats, saying at the time they were targeted because of ongoing harassment of U.S. personnel in Russia.

But at least some of the 35 diplomats were kicked out because they were suspected of being involved in election-interference operations, according to one of the former officials.

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The Russians were given 24 hours to get out of the compound and 72 hours to leave the country. Current U.S. officials tell CBS News they vacated the compounds before the 24-hour deadline, striking some as odd and raising the question of whether the diplomats had been tipped off about their expulsion.

Among the destroyed materials discovered at the compounds were antennas, electronics, computers, file cabinets and other gear, according to a former official. Other material was missing.

While the Russians would have been expected to destroy intelligence and equipment before leaving the country, the revelation raises the significance of the compounds in connection with Russia's election-interference operations.

In December, President Barack Obama said the compounds were "used by Russian personnel for intelligence-related purposes." Current and former officials describe the facilities as significant listening posts and centers of intelligence gathering, backing up concerns that they were part of the election interference infrastructure.

Last month, the Washington Post reported that the Trump administration was moving toward handing back the compounds. The Senate last week passed a bill in a 98-2 vote that would impose additional sanctions on Russia for its election activities. The measure includes a provision requiring congressional approval over any move by the administration to return the compounds back to the Russians.