LOS ANGELES (CNS) — More than 180 Los Angeles city firefighters with an assist from the LA County Fire Department knocked down a major emergency blaze that burned at least five businesses in a one-story row of commercial units in the Boyle Heights area Monday and left four firefighters injured.

The fire started around 2:30 p.m. at 2843 E. 11th St., according to the Los Angeles Fire Department.

At least one unit sustained a partial collapse, and firefighters remained in a defensive mode, officials said.

Three firefighters encountered an electrical hazard and were being evaluated by paramedics on scene. All three appeared to be in good condition, the LAFD reported.

A fourth firefighter suffered injuries from falling debris, LAFD spokesman Nicholas Prange said. All four firefighters were taken to a hospital, he added.

The department dispatched more than 180 firefighters to the scene along with 19 engines and 13 trucks, Prange said. All active flames were extinguished in two hours.

No other injuries were immediately reported.

The cause of the fire was under investigation.