MILWAUKEE (AP) — A child and two adults were missing after they were swept away in a drainage ditch in Milwaukee following severe thunderstorms that brought heavy rains and damaging winds to a wide swath of the Midwest, authorities said.

Witnesses told police the 11-year-old boy fell about 6:30 p.m. Monday into the ditch, which carries water through a tunnel to the Kinnickinnic River. According to police, two men, ages 34 and 37, entered the water in an attempt to rescue the boy and all three were swept away.

“In that tunnel, we have no idea what was going on in that tunnel,” said Assistant Fire Chief DeWayne Smoots.

Crews didn’t enter the tunnel due to dangerous conditions and instead sent a drone inside in an attempt to locate them, officials said. The water was deep and fast-flowing following Monday’s severe storms, which also caused damage in Illinois, Indiana and Michigan.

The storms came as high temperatures and humidity settle in over states stretching through parts of the Gulf Coast to the Great Lakes and east to the Carolinas. More than 100 million people were facing combination of heat advisories, excessive heat warnings and excessive heat watches through Wednesday following record weekend temperatures in parts of the West and the Southwest.

In Milwaukee, the fire department’s dive rescue team and the police department’s underwater dive rescue team were among first responders following reports that the three people were missing.

Crews ended their search late Monday and planned to resume their work Tuesday morning. Names of the missing weren’t immediately released. Police said all three knew each other, but didn’t elaborate.