"The first thing they heard was 'Help!'" said Adel Hagekhalil, assistant general manager of the sanitation department.
Workers lowered a hose down to the boy and pulled him up.
Jesse was taken to a hospital, although it was unclear whether he was injured.
"Any subterranean location, particularly one that involves waste, can produce toxic gases - methane, hydrogen sulfide - so breathable air is a key element", Humphrey said. "First thing [Jesse] wanted was a cell phone to call his family". Family members wrapped in blankets stayed at the search command post overnight.
The pipe was too unsafe for rescuers to enter, authorities said, so they set up at different drainage areas in hopes of finding where the boy would be flushed out.
"The expertise of the Bureau of Sanitation was instrumental in this search", Stewart said.
While jumping on one, authorities say, Jesse fell through.
Jesse's family was picnicking nearby as part of its annual Easter tradition before the boy went missing, fire department official said.
"They never gave up hope", he said. He fell into a sewage system that led to the L.A. River.
"We are so pleased and happy to announce a successful outcome", said Fire Capt. Erik Scott at a pre-dawn news conference. Cameras that are normally used for pipe inspections and can both float and crawl were sent into the pipes.
The pipes in the network are 4 feet in diameter and filled with 2 feet or more of sewage flowing about 15 miles per hour, the fire department said.