Russian hackers reportedly breached the voting systems of 39 states ahead of the 2016 election, according to Bloomberg, far more than previously known.

The revelation intensifies pressures on the Trump administration to adequately respond to a foreign actor threatening the integrity of the American democratic process—a move President Donald Trump has so far appeared unwilling to take.

The Bloomberg report builds upon reporting from the Intercept, which published a leaked National Security Agency document showing that the intelligence agency may believe Russian hackers infiltrated a voting software system and attempted to gain access to the accounts of more than 100 state election officials.

More than simply waging phishing attacks or spreading fake news and other misinformation to sway the American electorate, Russian hackers reportedly “tried to delete or alter voter data” in Illinois, according to Bloomberg, whose reporters spoke to three unnamed sources with knowledge of the alleged intrusions. While the report does not name all the states affected, it clarifies that 37 states found evidence of hackers in their systems. Two states, Florida and California, the hackers reportedly breached the systems of private firms that managed portions of the states’ voting systems.

The Obama administration was reportedly concerned that the hackers would attempt to delete voter registrations or hamper the voting process to undermine it. Former President Barack Obama reportedly contacted the Kremlin through the White House “red phone” back channel to present its evidence of Russian hacking directly. Despite the president’s push-back, the hacking reportedly continued.

“Last year, as we detected intrusions into websites managed by election officials around the country, the administration worked relentlessly to protect our election infrastructure,” Eric Schultz, an Obama spokesman, told Bloomberg. “Given that our election systems are so decentralized, that effort meant working with Democratic and Republican election administrators from all across the country to bolster their cyber defenses.”

During testimony before the Senate Intelligence Committee on June 8, former FBI Director James Comey assured senators that Russia did attempt to meddle in the 2016 election and that it will likely do so again.

“They did it with overwhelming technical efforts, and it was an active-measures campaign driven from the top of the government,” Comey said. “That’s about as un-fake news as you can possibly get.”