Inside a Port of Seattle warehouse Wednesday afternoon, Seattle police officers spent hours training for May Day. 

In recent years, Seattle police have seen May Day marches start peacefully, but end in violent clashes with both police and protesters getting hurt.

Captain Chris Fowler will serve as the Incident Commander on May 1.  

"I think given the current climate, we may have more people," said Fowler about the number of potential protesters.

Fowler added that he knows of as many as four groups, gathering in different parts of the city that will likely converge with the immigration march. He said so far, the immigration march is the only permitted May Day event.

During Wednesday's training session, some officers posed as protesters while patrol and bike officers tested out tactics. 

"We want to keep everybody safe," Training Captain Bryan Grenon said. "The only way we can do that is to go out and actually practice multiple times to make sure everybody from the officers all the way up the chain understand what we are doing and what we are trying to accomplish."

Last year, police say an officer was hit with a Molotov cocktail, an incendiary device. As a result, this year some officers will carry Cold Fire Tactical, a fire extinguishing agent.

Lt. Marc Garth-Green says if necessary police could also deploy pepper spray and use blast balls. Blast balls are used, depending on the level of violence during a protest, to disperse the crowd, according to Garth-Green. Blast balls deliver a stimulus of sound and light, and small fragments can come off. In the past, protesters have complained about being injured by blast balls.

"With the unpermitted marches, we are there to support the exercise of free speech," Fowler said. "Once that turns dangerous or violent or infringes on other people's rights, then we'll take a tactical response based on what the crowd is doing."