Portland bar owners and other merchants are being warned not to allow customers wearing gang colors and other insignia into their establishments following a fist fight involving two dozen motorcycle gang members on Commercial Street early Saturday evening.

Two men were arrested and two were treated for injuries at local hospitals after the brawl between members of three rival motorcycle gangs broke out shortly after 6 p.m. at the corner of Union Wharf and Commercial Street.

Jeffrey Vandermeiren, 43, of South Portland was arrested for disorderly conduct and Thomas Glaude, 52, of Waldboro was arrested for failing to disperse. Police would not identify which gangs were involved.

Portland police said they have stepped up their patrols and the Portland Downtown District merchants association has urged merchants to be vigilant against in efforts to control gang-related activity.

“To say this type of fighting and injury is bad for our image especially during the tourist season is an understatement,” Janis Beitzer, executive director of the Portland Downtown District, wrote in an email sent to members Wednesday.

Portland Police said there is no reason to expect a return of violence that erupted during an Old Port turf battle between motorcycle gangs eight years ago when then-Police Chief Michael Chitwood announced a crackdown on gang activity in Portland.

Since then motorcycle gang activity has mostly disappeared.

Lt. Gary Rogers said there were no weapons involved in Saturday’s brawl, unlike the fighting eight years ago. He said the fight was unusual because it took place in broad daylight when tourists and families were about.

“Usually this stuff happens after 11 p.m.,” Rogers said.

Acting Police Chief Michael Sauschuck said he is stepping up patrols and taking other precautions to make sure the violence does not return.

Some area merchants said the incident was probably isolated. Charles Bryon, owner of the Salt Exchange restaurant on Commercial Street said he was unaware of any fighting until about a dozen police officers descended on the nearby scene.

He said he is more concerned about panhandlers and inebriated people wandering the streets than of gang violence.

Tanner Herget, owner of the 51 Wharf Restaurant and Ultra Lounge and FortiFem Martini Lounge and chairman of Old Port’s Night Life Oversight Committee, said fighting is rare at Portland’s bar scene these days.

He said many bars have dress codes and security at the door. His own bar turns away about a third of those trying to enter.

“We say casual chic and fashionable radiate good energy,” said Herget.