Crews dredged the drought-shrunken Mississippi River around the clock Thursday to free hundreds of backed-up barges, while triple-digit temperatures prompted autoworkers to walk off the job after a co-worker collapsed and died.

Sprinklings of rain Wednesday succeeded only in frustrating farm-belt growers, many of whom urged federal action and said two more weeks without a drenching could plunge them into disaster."With the searing heat we've had the situation has become very, very serious as our crops begin to deteriorate," said Iowa's secretary of agriculture, Dale Cochran. "In the next 10 days, if we don't get rain we could lose 50 percent of our corn crop."

In Fenton, Mo., a Chrysler Corp. autoworker died after collapsing Wednesday night in what co-workers said was unbearable heat in a paint shop, as temperatures in the St. Louis area topped 100 degrees.

"It's so hot, you can hardly breathe in there. It's like you're smothering - like you're inside an oven," said one worker, Bertha Saxton. "Your skin is like someone poured baby oil on you."

An autopsy on Willie Benton, 54, was to be performed Thursday, said Suzanne Campbell, spokeswoman for St. Joseph Hospital, where Benton died.

Shortly after he collapsed, hundreds of paint-shop workers at Chrysler's No. 1 and 2 plants walked off their jobs because of the heat. The walkout, the second in two days, forced the assembly lines at both plants to shut down.

Also Wednesday, the Coast Guard for the first time limited the number of barges towboats can push in a major portion of the Mississippi. The limits were sought by barge companies that want to prevent towboat operators from running their loads aground in record-low water.

"There's got to be a doomsday point out there somewhere. Right now, I don't know anybody that I've talked to who can give me any idea where that is," said Brig. Gen. Thomas Sands, president of the Mississippi River Commission. "Right now, we are not on the brink of disaster."

U.S. Agriculture Secretary Richard Lyng planned to meet in Chicago Thursday with representatives of drought-stricken states to advise a committee of the National Governors' Association on the crisis and the outlook for the nation. The governors were expected to prepare recommendations.

The day before, Lyng met in Washington with a congressional drought task force, which urged him to take all steps in his power to provide relief.

Rep. David Nagle, D-Iowa, said the focus of immediate efforts is on assuring feed for livestock and that legislative action to deal with crop losses would be delayed until officials determine the extent of the damage.

The record-setting heat wave continued to quicken the evaporation of moisture from the soil, but temperatures began to drop and the National Weather Service predicted some temporary relief Thursday.