Tony Pierce / KPCC

A man wearing a Joker mask listens to speakers at a May Day rally in Pershing Square

DOWNTOWN LOS ANGELES — Thirteen people were arrested and two LAPD officers were injured following the May Day march that brought protestors of many different interest groups including LGBT and a heavy concentration of "Occupy" protesters to Downtown Tuesday.

LAPD officer Christian Lata could not confirm what the charges were for those arrested, but did say that two suspects were wanted in connection with striking officers with a wooden palette.

“It was very cowardly the way they did it,” Lata said, explaining that the suspects waited until the officers had turned their backs to attack.

Also injured was a female officer who was taken to a hospital after being struck in the back of the head with a steel drum, Lata said.

The officer was struck so hard it broke her Kevlar helmet, which is used to help stop bullets, officials said. She suffered a semi-concussion and is now at home resting according to LAPD Chief Charlie Beck who spoke to media Wednesday.

Other than the two incidents, Beck said it was a mostly peaceful May Day.

"There were thousands of people that did this the right way and they got their message across and individuals like this detract from that," Beck said at the LAPD headquarters.

Though they admitted there were a few arrests, the Occupy Los Angeles movement sent out a tweet last night saying the march "was very successful and mostly peaceful."