MADISON, Wis. — Hackers stole $2.3 million from the Wisconsin Republican Party’s account that was being used to help reelect President Donald Trump in the key battleground state, the party’s chairman told The Associated Press on Thursday.

The party noticed the suspicious activity on Oct. 22 and contacted the FBI on Friday, said Republican Party Chairman Andrew Hitt.

Hitt said the FBI is investigating. FBI spokesman Leonard Peace did not immediately return a message seeking comment.

The attack was discovered less than two weeks before Election Day as both Trump and Democratic rival Joe Biden made their final push to win Wisconsin and its 10 electoral votes. Trump won the state by fewer than 23,000 votes in 2016 and planned his third visit in seven days on Friday. Biden also planned to campaign in Wisconsin on Friday. Polls have consistently shown a tight race in the state, usually with Biden ahead by single digits and within the margin of error.

Hitt said the stolen money would have been used in the final days of the campaign to make snap spending decisions based on the state of the race.

He said the hackers manipulated invoices from four vendors who were being paid to send out direct mail for Trump’s reelection efforts and to provide pro-Trump material such as hats that could be handed out to supporters. Invoices and other documents were altered so when the party paid them, the money went to the hackers instead of the vendors, Hitt said.

The Money Was Stolen From the State Party’s Federal Account

The hack was discovered after someone noticed that an invoice was generated that should not have been, he said.

Hitt said it appears the attack began as a phishing attempt. It does not appear that any data was stolen, said party spokesman Alec Zimmerman.

The money was stolen from the state party’s federal account, which currently contains about $1.1 million, but that number fluctuates daily because of quick moving resources late in the campaign, Zimmerman said.

Hitt said he was not aware of any other state GOP being targeted for a similar hack, but state parties were warned at the Republican National Convention this summer to be on the lookout for cyber attacks.

Campaign finance reports filed this week in Wisconsin show Democrats have raised far more money than Republicans. The state Democratic Party raised nearly $59 million over the past two years compared with just $23.7 million for Republicans.

Early voting is in full swing in Wisconsin, with more than 1.6 million ballots returned as of Thursday morning. That is nearly 55% of the total vote cast in 2016.