Olive and Philip Chong had their Saturday all planned out: a relaxed breakfast followed by Christmas shopping. That changed drastically around 9 a.m., when their daughter stopped on the stairs leading to the basement of their home, a basket of laundry in her hands.

Swirling around the washer and dryer, she saw two inches of greenish brown water. The rancid smell that hit her next let her know what kind of water it was: raw sewage. She retreated back upstairs.

Olive Chong said her daughter announced that even though it was cold out, they needed to open the doors and windows. “The stench was so bad that my daughter said to me, ‘We gotta’ air this place out.’”

The Chongs soon found out they weren’t alone. Word spread quickly around the South Jamaica neighborhood of modest homes on small lots, of chain link fences and TV antennas sprouting from roofs with sun-bleached shingles, that just about every resident on more than a dozen blocks had the same problem.

The NYC Department of Environmental Protection said the issue impacted "homes in the vicinity of 133rd Avenuve and Inwood Street."

Stinky situation in Queens after sewage water started filling people’s basements earlier today - homeowners are using pumps and buckets to get dirty, smelly water out. As many as 400 homes affected - cause unclear @NBCNewYork pic.twitter.com/YFxZ9nez6A — Anjali Hemphill (@AnjaliHemphill) December 1, 2019

The cause, they’d come to find out, was a blockage in a large city sewer pipe that parallels nearby Belt Parkway. Liquid sewage usually moves through the line and ends up at the Jamaica Wastewater Treatment Plant. But now it was hitting the blockage, reversing course, and inundating area basements.

Ted Timbers, a DEP spokesman, said more than eighty homes in South Jamaica had been flooded, and contaminated, in this way. “But it could be more than that,” he noted on Sunday. “There are 300 homes in the affected area and some of those people could’ve been away for the weekend and only finding out now.”

City sanitation crews barricaded several blocks and pumped out basements throughout the weekend, spilling pungent sewage through bulging hoses into the street. “We'll get some assistance from the rain,” Timbers said. “It should wash the residual wastewater from the roadways and sidewalks in the impact zone.”

DEP workers also used hoses to reroute local wastewater into sewer lines that were not clogged. The efforts stabilized the situation. But crews were still working as of Sunday night to clear the blockage that caused the problem. Timbers said the city didn’t know what was stuck in the pipe but noted that, “Fat, oil, and grease are the number one cause of sewer back-ups in the city.”

It was the not-knowing that worried Philip Chong. “What caused this thing to happen?” he asked while standing in his slightly malodorous kitchen. “Will it be happening again? It’s not a nice situation.”

Here’s one homeowner in Jamaica Queens pumping sewage water out of her basement. She’s been at it for almost 24-hours. @PIX11News pic.twitter.com/DfWOjoGSQ8 — jennbisramtv (@jennbisramtv) December 1, 2019

At the city’s request on Saturday, the Red Cross set up a hastily organized relief center in nearby PS 223. Red Cross spokeswoman Desiree Reiner said residents began arriving soon after the doors opened. “Between 60 and 80 families have come through here, asking for information,” she said. “Some people needed food. A couple of families needed a place to stay.”

A woman exiting the school with a Red Cross kit full of cleaners and disinfectants was too distraught to speak to a reporter. Now that the wastewater has been pumped out of homes, owners have a mammoth task ahead. First, they must scrub the feces from their basements, then deal with insurance.

The DEP sent command buses to the neighborhood to hand out forms for homeowners to file damage claims with the city.

Jim O’Grady is a news reporter for WNYC. You can follow him on Twitter at @jimog.