Camden Yards' policy forbids banners, which can obstruct views. Also, banners can be confiscated if their message is commercial, political or 'in bad taste'

Trump repeatedly disparaged Baltimore - a city represented in congress by Elijah Cummings, who's leading multiple investigations of the president

Many of the fans in attendance were chanting 'take it down,' according to the Sun and several attendees who wrote about the incident on social media

Seated in the front row of the upper deck at Camden Yards, the four fans unrolled the banner which read 'Keep America Great!' and 'Trump 2020'

A 'Trump 2020' banner was unfurled at Thursday's Baltimore Orioles game, resulting in the ejection of four fans who were in violation of stadium policy

After days of President Donald Trump publicly quarreling with congressman Elijah Cummings and his home city of Baltimore, a 'Trump 2020' banner was unfurled at Thursday's Baltimore Orioles game, resulting in the ejection of four fans who were in violation of stadium policy.

Seated in the front row of the upper deck at Camden Yards, the four fans unrolled the banner with the words, 'Keep America Great!' and 'Trump 2020,' in the eighth inning of the Orioles' 11-2 loss to the visiting Toronto Blue Jays.

A photo taken by a Baltimore Sun reporter at the game shows the fans unveiling the banner. They were approached by security roughly 10 minutes later and removed from the stadium.

Many fans in attendance could be heard chanting 'take it down,' according to the Sun and several attendees who wrote about the incident on social media.

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Seated in the front row of the upper deck at Camden Yards, the four fans unrolled the banner with the words, 'Keep America Great!' and 'Trump 2020,' in the eighth inning of the Orioles' 11-2 loss to the visiting Toronto Blue Jays

'A "take it down" chant broke out at Camden Yards as this was unveiled in the eighth inning tonight,' Tweeted the Sun's Orioles beat writer, Jon Meoli. 'The banner has not been well-received.'

'Trying to enjoy my time at @Orioles and having to deal with this nonsense,' wrote state representative Charles E Sydnor III on Twitter. 'Many Baltimoreans chanting to take it down.'

'Let's just say #MAGA is not the @Orioles slogan,' wrote on Twitter user. '"Take it down" chants in the background.

Camden Yards' policy says no banners can be hung in the stadium to keep from obstructing views, and that banners can be confiscated if they're commercial, political or 'in bad taste'

Camden Yards' policy says no banners can be hung in the stadium to keep from obstructing views, and that banners can be confiscated if their message is commercial, political or 'in bad taste.'

In tweets and comments, Trump repeatedly disparaged the storied Maryland city and majority-black district represented by the Democrat, who's leading multiple investigations of the president's governmental dealings.

On Friday Trump shared the 'really bad news' that Cummings had his home burglarized in Baltimore.

According to Baltimore police, Cummings home was burglarized at 3:40am Saturday – just hours before Trump began teeing off on Cummings and his 'rat-infested' district.

'Really bad news! The Baltimore house of Elijah Cummings was robbed. Too bad!' Trump wrote Friday morning.

President Donald Trump has been publicly quarreling with congressman Elijah Cummings and his home city of Baltimore for several days

Representative Elijah Cummings, a Democrat from Maryland and chairman of the House Oversight Committee, has been at odds with Trump over his criticism of Baltimore

A similar incident occurred in Boston on Thursday when fans unveiled an anti-ICE banner over the Green Monster in Fenway Park.

'No ICE. No Prisons, No More Cages,' the black banner read

Fenway Park's code of conduct permits signs and banners inside the historic ballpark, but has an absolute ban on any signs from being hung over the Green Monster.

'Management reserves the right to remove any signs or banners at any time,' the code of conduct says.

The activists were promptly escorted out of the park by officials.

Those behind the political protest were part of the groups 'Deeper Than Water' and 'Black and Pink'.

'Deeper Than Water' is an activist group which describes itself as 'an abolitionist coalition working against incarceration and water injustice in MA (and across the world).'

The group posted on Facebook after the protest: 'Activists with 'Deeper Than Water' and 'Black and Pink' send a message to the American Correctional Association during the Boston Red Sox Game: NO ICE, NO PRISONS, NO MORE CAGES.

'The ACA's conference of prison profiteers is in Boston and we are demanding: 1. Shut down the cages and the camps 2. Stop accrediting facilities that abuse people and violate human rights 3. Make the credentialing process public.'

The ACA, which plays a part in establishing ICE detention facility standards, will continue its annual conference in Boston this week.