The National Weather Service began sending flash flood warnings that should have triggered cellphone alerts a little after 1 a.m., while local officials began posting on Facebook about four hours later.

The downpours that swept away a children's summer camp and wreaked deadly havoc on huge areas of Texas caught holidaymakers by surprise. As the death toll passes 90 people, questions are being raised about whether adequate flood warnings were provided and why people weren't evacuated ahead of the deluge.

Flash floods in Texas have killed more than 100 people, many of them children. Heavy rains fell quickly in the predawn hours Friday in the Texas Hill Country.

Parts of the state devastated by flash floods that left at least 82 dead were braced for more heavy rains as forecasters extended flood warnings through Monday evening.

With more rain on the way, the risk of life-threatening flooding was still high in central Texas on Monday even as crews search urgently for the missing.