Crews are searching for the bodies of a man and a woman who were presumed drowned when they tried to rescue six-year-old Garrett Wallace after he fell into the icy Big Sioux River in South Dakota.

Garrett slipped into the icy river in Sioux Falls around 6 p.m. on Thursday while playing under a pedestrian bridge inside a park, the Argus Leader reported.

The boy was able to get out of the fast-moving, icy river, but his sister and a man disappeared into the waterway while trying to rescue him, the Associated Press said. The Argus Leader identified Garrett’s sister as Madison Wallace, 16, and the man as Sioux Falls resident Lyle Eagletail, 28.

The search for the bodies continued on Friday.

Napoleon Ducheneaux said he witnessed his friend Eagletail fall into the river while trying to help Madison and her brother. He said Garrett might not be alive had it not been for their efforts.

"These people literally jumped in without thinking of their own safety and trying to rescue that child," he told the AP. "It's a very noble act that they did, and they probably contributed to saving that boy's life."

Sioux Falls Fire Chief Jim Sideras told the news wire service that Garret hadn’t been in the icy river “that long.”

He said crews are battling strong currents and thick sheets of ice amid the search-and-recovery rescue operation. They’re also risking hypothermia, Sideras said.

The Big Sioux River also has large amounts of foam, the AP said, and firefighters are trying to combat the problem by blowing it away with water hoses. The ice is another big obstacle, the Argus Leader said, noting that a dive team deployed in an effort to recover the bodies can’t begin their search until the ice is broken up.