2012 'May Day' Protests From Coast to Coast Occupy protesters and labor, immigration activists protest on May 1.

May 1, 2012  -- Stinging gas has caused 'May Day' protesters to flee downtown Oakland and police detained at least six people in New York as Occupy demonstrators and labor and immigration activists participated in "May Day" protests across the country on Tuesday.

Protest organizers said they intended to show the "1 percent" what life without the "99 percent" would look like, as they encouraged workers and students to take a day off in solidarity against income inequality and "unjust" corporate practices.

Police in Oakland took at least four people into custody on Tuesday though it is unclear if police fired the gas as several hundred protesters blocked traffic near Oakland City Hall, the Associated Press reported.

ABC New York affiliate, WABC, reported that four protesters were detained during the march across Williamsburg Bridge, connecting Brooklyn to Manhattan, and at least two protesters were detained in Midtown Manhattan.

An estimated 200 protesters are in Madison Square Park in New York City, while another 500 people are in Bryant Park. In Chicago, an estimated 1,000 people have gathered in a section of Union Park despite occasional rain, the Chicago Tribune reported. There have been an unknown number of arrests in Philadelphia and Los Angeles International Airport related to the protests.

As letters containing white powder, later determined to be non-toxic, arrived in mail rooms of Manhattan banks and New York's City Hall, a wide range of protesters gathered around the buildings of corporations and city centers across the country.

The FBI announced on Tuesday that that they arrested a group of anarchists who allegedly plotted to use explosives to blow up a bridge near Cleveland, Ohio and attack this summer's Republican National Convention in Florida. The FBI's criminal complaint does not state the attacks were planned as part of the May Day protests.

Pete Dutro, an Occupy organizer from Brooklyn, N.Y., said the date of the nationwide strike is related to the Haymarket massacre in Chicago. Demonstrators were protesting on May 4, 1886 in favor of an eight-hour workday when a bomb was thrown, killing both police and workers. Some labor groups recognize May 1 as "International Workers' Day."

"Without labor, we do not produce things. That's kind of why this started," Dutro, 37, said. "The labor conditions were not good back then, people were being exploited and you had a huge disparity in income. And that's what we're facing right now."

Dutro, a part-time tattoo artist and former grad student studying finance, said he became involved early on in the Occupy Wall Street movement because of his personal experience as a business owner and his struggle to pay for health care.

Diagnosed with testicular cancer in 2004 and not able to afford health insurance, Dutro said he had to close his two businesses, a tattoo shop and web design company. He said they together employed 25 people.

"I was a real job creator, but at that point in my life I could not afford health insurance and the cost of living and running a business was outrageous," he said.

Dutro and the other Occupy Wall Street protesters were cleared out of Zuccotti Park in November, two months after they began their encampment, and protesters have since been forcibly removed in cities across the country.

Andy Thayer, a Chicago Occupy member and the spokesperson for the Coalition Against NATO/G-8, called this year's strike "a national phenomenon" with immigration rights advocates partnering with the Occupy movement.

"There's a good buzz about it -- the kind of display not been seen in many decades: a demonstration of solidarity on immigrant rights, but also about labor's winning back rights or winning rights anew," Thayer said.

Events are taking place at all hours of the day, from Los Angeles to Chicago to New York.

In New York, community groups, unions and Occupy Wall Street protesters converged at a number of locations starting at 8 a.m., including the Chase Building, New York Times Building, Sotheby's, and a U.S. post office. Protesters planned to march over the Williamsburg Bridge from Brooklyn to Manhattan after meeting in Continental Army Plaza at 10:30 a.m.

Dutro said some events are taking place without a permit, like a guitar workshop in Bryant Park, which he expects will attract attention from the police.

"Everything's been really crazy," Dutro said, in reference to the planning leading up to May 1. "People are coming back to town, asking what's going on."

Dutro said he received 200 emails on Monday about the events.

"It's a nightmare," he said.

Dutro said he has been coordinating with protesters in other cities, including Los Angeles. There, a strike at Los Angeles International Airport is scheduled for 6 A.M. in conjunction with some members of the Service Employees International Union and United Service Workers West.

Another protest event in Los Angeles, dubbed, "Let Them Eat Cupcakes," is planned for tony shopping area, Rodeo Drive, around noon.

In Chicago, gatherings include a protest at noon in Union Park, followed by a march downtown at 1 p.m.

Thayer said there is "special urgency" in Chicago related to Chicago's NATO summit on May 20 to 21. Later in May, Thayer said there will be a mass march led by veterans against war who will be turning in their medals in Grant Park.

The Federal Protective Service, which guards federal buildings, announced last week that there will be protective "Red Zone" around Chicago's downtown federal buildings this week in advance of the summit.

The Chicago Tribune reported that the officers will carry non-lethal weapons.

Thayer called the security plan "totally over the top," and said it reminded him of the security detail for the "Trans Atlantic Business Dialog" which took place in 2002.

"They looked like Ninja Turtles. It was such an offensive display of hardware it was frightening to kids," Thayer said, adding that 'the latest display by the Feds" will "give people a taste of what life is like in other countries on a regular basis -- troops in the streets for weeks at a time. It breeds real resentment. Chicagoans are p.o.'d that this is taking place in conjunction with the May Day march."

When asked if the nationwide protests, which are aiming to disrupt the work day and commuting, risk alienating workers who are not participating in the day's events, Dutro said he would sympathize with their frustration.

But, "by complaining, I would say you further help others that maintain the status quo, and what is clear is the status quo is not working," he said. "Yes, they have families and have to work and all these other things. But in the greater scheme of things, if we don't solve these problems now there will be less and less work to go to."

ABC News' Richard Esposito contributed to this report.