WATTS -- Los Angeles police have surrounded a home in Watts in search of a gunman who shot an officer in the arm during a welfare check.

It happened near Lou Dillon Avenue and 107th Street just before 2:30 a.m. Friday. Officers went to the house to investigate reports of a possible hostage situation, according to Officer Norma Eisenman. When police arrived, someone came out of the home and assured them everyone was fine.

The officers went in anyway to check on the situation and a gunman immediately fired shots at them. The officers fired back and ran out of the house after one of them was shot once in the arm. The wounded officer was transported a local hospital for treatment. He was said to be greeted by family and LAPD Chief William Bratton. The officer, a 4-year veteran of the force, is expected to survive.

Investigators said he was also shot in the chest, but his bullet-proof vest saved his life. A SWAT team has surrounded the house to try to get the gunman to surrender. It was possible the gunman was wounded when officers initially fired back, investigators said. No other suspects were being sought.

Three people who exited the home were detained for questioning but were not considered suspects in the shooting, Eisenman said. Police were using high-tech equipment to detect any movement inside the house and begin negotiations with the suspect. Officers were also preparing to forcefully enter the home if necessary.