Michigan, a battleground state that will help determine who wins the U.S. presidential election, is still counting "tens of thousands" of ballots, according to a top state official.

Emotions were running high in Detroit, where poll watchers were barred from the counting room on Wednesday afternoon.

Republican President Donald Trump narrowly won Michigan in 2016 but late on Wednesday, major news organizations projected that Democratic challenger Joe Biden won the state. Trump has made clear he will fight to challenge the results there.

"We know that tens of thousands of ballots are still outstanding and need to be tabulated" in Detroit, Grand Rapids, Flint, Kalamazoo and other cities, Secretary of State Jocelyn Benson said in a Wednesday morning news conference.

She said the outstanding vote count was just over 100,000, with most being absentee ballots.

With 99% of the vote counted, Biden held a lead of just over 60,000 votes, according to the Detroit Free Press.

Benson told the news conference she was confident the state's election process could withstand a legal challenge. Nevertheless, Trump's campaign later filed a lawsuit seeking to stop the count in Michigan, asserting it had not been allowed to observe the opening of ballots.

Emotions were running high Wednesday afternoon in downtown Detroit, where city election officials blocked about 30 people, mostly Republicans, from entering the vote-counting hall at TCF Center due to capacity restrictions to fight the spread of COVID-19.

Democrats said they had also been barred. One poll worker told Reuters that Republicans were "trying to slow down and obstruct the counting."

Detroit police were called to enforce the decision, and some of those barred from the hall grew agitated when poll officials blocked the windows with pizza boxes and cardboard to prevent challengers from viewing inside.

Many stood outside the hall voicing their protest and singing "God Bless America," while a second group of Republican election challengers who had been denied entry gathered in a prayer circle outside the convention center and also chanted "Stop the vote" and "Stop the count."

Greg King of the Trump campaign said the problem arose when people left for lunch and did not sign out. When they returned, it created the appearance of too many people in the room.

Democratic poll observer Liz Linkewitz said she and other Democrats had been barred, as well, and it was not a partisan issue.

“I'm very upset," said Sherman Rogers, 53, a Republican who was among those barred from entering.

A city election commissioner later came out and explained that controlling the number of people in the room was necessary to protect against the coronavirus, and there were still poll challengers from all parties in the hall. He left after people kept shouting over him.

Benson earlier said she was optimistic the majority of ballots cast on or before Election Day will be tabulated in an unofficial count by the end of the day.

"The number of outstanding ballots is still greater than the margin of difference in many races," Benson said. "Our goal is to ensure that we are being transparent, but also fully accurate."