CEDAR RAPIDS, Iowa — Rescue crews peered beneath manhole covers, used sonar in a lake and deployed divers in the search for a teenager who was swept away in a Cedar Rapids storm drain after rainfall overwhelmed the eastern Iowa city's sewer system.

Logan Blake, 17, somehow ended up in the drain while playing Frisbee with friends, said city public safety communications coordinator Greg Buelow.

Buelow and Cedar Rapids Fire Department Battalion Chief Brian Gibson said Tuesday they still considered the operation a rescue mission.

David Bliss, 17, tried to save Blake but was also dragged into the drain. That teen traveled along the drain for more than a mile, eventually emerging in Cedar Lake. The boy walked to a hospital and was treated for non-life-threatening injuries.

Fire department crews were using sonar and boats to search the body of water. A dive team also went in the lake, while officers with dogs and about 60 volunteers searched along the path of the pipe by foot.

Buelow said the storm drain feeds into an underground concrete pipe about 4 1/2 feet wide at the school's culvert entrance. That pipe runs about a mile and a half southwest and is 10 feet in diameter where it empties into Cedar Lake.

One expert questioned whether the drain complied with safety criteria recommended for the industry, and said the teen's disappearance was part of a national problem.

Any drain that is wider than 48 inches or long enough that one cannot see daylight at the end should generally have a safety grate, said Ken MacKenzie, a committee chair for the National Association of Flood & Stormwater Management Agencies.

"If there was a 54-inch diameter pipe next to an elementary school without a safety grate on the inlet, that was a dangerous situation that could have been prevented." he said.

Craig Hanson, director of the Cedar Rapids public works department, said the drain had been there for decades without a problem. He said, to the city's knowledge, it's never had a grate, in part because of fears that it could get clogged and flood the neighborhood. The city probably will review the safety of its system, he said.

Blake's father, Mark Blake, told ABC News that the family was holding out hope that he would be found alive.

"He's a strong kid, a very athletic kid," he said. "He's got a strong will. We have every faith in the world that he's hooked on and waiting for the current to slow down."