HOBOKEN -- Thousands of revelers dressed in green invaded Hoboken Saturday for LepreCon, the annual St. Patrick's Day pub crawl.

More than 25,000 people are expected at the all-day long event, according to Hoboken Police Chief Ken Ferrante.

Organizers said more than 20 bars were participating in the event, now in its fifth year. LepreCon replaced the city's annual St. Patrick's Day parade after officials decided to cancel it in 2012.

Ferrante said 50 extra officers were launched at noon, and by the end of the day, more than 200 officers will be patrolling the streets of Hoboken.

"This is their most challenging day but they are ready!" Ferrante tweeted about the officers.

Although things were relatively calm by 12:30 p.m., Ferrante said he expects some trouble.

"With 2500 people, mostly intoxicated, officers expect challenges," Ferrante said. "And some bizarre instances."

Last year, a heavily intoxicated homeless man set himself on fire in the middle of the street in the evening, Ferrante said.

As of 6:30 p.m., Ferrante said about 25 summonses were issued, 16 people were sent to the hospital and six people were arrested.

One of those arrested was a drunk and disorderly man who spit on a county officer and a 25-year-old from Bernardsville who assaulted a nurse at Hoboken University Medical Center.

Several house parties were also shut down and summonses were issued.

Fausto Giovanny Pinto may be reached at fpinto@njadvancemedia.com. Follow him on Twitter @FGPreporting. Find NJ.com on Facebook.