A recovery operation is underway after 10 people were washed away by a swift current in an Ontario storm drain amid heavy rains Tuesday, and up to four of them remain missing.

The incident was first reported around 9:50 a.m. on 4th Street near John Galvin Park. The operation is now focused on East Philadelphia Street and Baker Avenue.

Ten people were reported to have been washed away by flood waters, Ontario Fire Department Chief Ray Gaul told KTLA.

Five people have been rescued and one man was confirmed dead, leaving authorities to search for up to four others. Two of them were seen in the water — though authorities are still searching for them — and two additional people were also seen in the water, but it is unknown if they escaped on their own or are dead in the basin.

They were previously described as being homeless and living in the area when the basin swelled with rain water during a powerful storm that slammed Southern California.

Video from the initial rescue operation showed the fast-moving current.

Fire officials are now focusing on finding two to four people believed to still be in the basin, and they vowed to continue their operation until they find them, Gayk said.

“We’re going to continue to search until the people are accounted for,” the chief said.

Bianca Laguna, the cousin of one of the possible victims, was at the basin Wednesday hoping the search turned up her loved one.

“We’re hoping that she’s alive and she’s safe,” Laguna said. “We just want her to come home.”