OKLAHOMA CITY (AP) - It was the most active week of tornadoes on record as scores of twisters ripped across the nation's midsection, reducing hundreds of homes and businesses to splinters and piles of loose bricks, meteorologists said Saturday.

The tornadoes combined with straight-line wind, lightning and floods to cause 44 deaths from Kansas to Georgia.

''We just don't have a down day; that's what's been very unusual,'' said Rich Thompson, lead forecaster at the Storm Prediction Center of the National Weather Service, in Norman, Okla. ''It just doesn't seem to stop.''

On Saturday, the weather service posted tornado warnings for parts of Indiana, Missouri and Illinois. And the Storm Prediction Center said severe thunderstorms were likely from eastern Oklahoma to western Ohio.

More than 100 people were injured in the Oklahoma City area by two tornadoes that struck Thursday and Friday night. One remained in critical condition Saturday.

President Bush issued a disaster declaration Saturday for Oklahoma, clearing the way for federal aid. Earlier in the week, he did the same for tornado-battered parts of Tennessee, Kansas and Missouri.

More than 300 homes and 35 businesses were destroyed in Oklahoma alone.

and the state insurance commissioner's office gave a preliminary damage estimate of $100 million. Utility crews strung new power lines in an effort to restore electrical service to more than 10,000 homes and businesses.

While tornadoes are common in May, the number of them reported in the first part of this month has been extraordinary, said Dan McCarthy, warning coordination meteorologist at the Storm Prediction Center.

By Saturday, about 300 tornadoes had been reported since the start of May, about 100 more than the most recent comparable rash, in 1999. Until now, that 1999 barrage had been the record for any 10-day period since record-keeping started in the 1950s, said Dan McCarthy, warning coordination meteorologist at the Storm Prediction Center.

About 70 percent of all tornadoes are reported in April, May and June.

''What is happening this week is that we have a persistent warm air mass in place and a persistent jet stream extending from the Southwestern United States into the central Plains,'' McCarthy said.

Those conditions were ripe for producing thunderstorms, which can rotate and form tornadoes.

Changing weather conditions were expected to reduce the risk beginning Sunday.

Because of the tornadoes and other emergencies this year, the American Red Cross said Friday its disaster relief fund, which typically has a $50 million cushion, had dwindled to just $5 million. Executive vice president Terry J. Sicilia estimated that the costs of the recent tornadoes could deplete the fund entirely if more donations don't come in soon.

The twister that struck the Oklahoma City area late Friday approached the metropolitan area from the southwest, then skipped through the city, snapping utility poles, flipping a light airplane parked at Wiley Post Airport and ripping apart an elementary school.

Damage was spotty. A mower repair shop near the airport was totaled, but nearby homes had only minor damage.

''From what we've seen there was significant damage, but it was not continuous, not widespread for a tornado moving through a major metropolitan area after dark on a Friday night,'' said Rick Smith, a weather service meteorologist.

Thursday's tornado blasted a 19-mile-long path through Oklahoma City's southern suburbs, injuring more than 130, destroying more than 300 houses and businesses and damaging hundreds more. Unlike Friday's twister, that tornado stayed on the ground for most of its route.