Police responded to a report of shots fired in the 1700 block of W. 70th Street, near 66th Street and Western Avenue, at about 2:45 p.m.
Two LAPD patrol officers had stopped to question a group of pedestrians, according to the department. When the officers got out of the car, someone fired a handgun, striking one of the officers three times. Two of the bullets hit the officer's protective vest and the third struck him in the hand.
That officer was hospitalized at California Hospital Medical Center in serious condition. The second officer was not struck, officials said.
Authorities said the officers exchanged gunfire with the suspects but it was unknown whether any of them were hit. They fled on foot in opposite directions.
A 72-block perimeter was set up to search for suspects between Gage Avenue to 76th Street, and from Arlington Avenue to St. Andrews Place. The LAPD set up a command post at Horace Mann Middle School at 7001 South St. Andrews Place.
Police reopened the area Thursday night after the hours-long search turned up nothing, but kept one street closed on 70th between Western Avenue and Harvard Boulevard to continue looking for evidence.
Police said one person of interest was taken into custody for questioning. A search for other suspects continued.
The two suspects at large were described as two black men approximately 18 to 25 years old. One was seen wearing a white shirt and black pants; the other was described as wearing a white shirt with long blue sleeves and dark pants.
Mayor Antonio Villaraigosa said the hospitalized officer was in stable condition.
The 77th Street Division officers were believed to be investigating car burglaries in the area, according to LAPD Chief Charlie Beck.
The officer was struck in the torso and had a contusion to his chest, according to a trauma doctor at California Hospital Medical Center.
"I can simply say the bulletproof vest played very good job in protecting his life," Dr. Gudata Hinika said. "The bullets that hit his chest could have entered his chest, but luckily they didn't because of the vest."
The officer reportedly began asking when he could return to work.
Beck said Thursday's incident marked the third time LAPD officers were shot at in the last seven days.