A man waits to check into the shelter in the George R. Brown Convention Center in Houston in the aftermath of Hurricane Harvey, Aug. 28, 2017.

The George R. Brown Convention Center in downtown Houston, the city's main evacuation center, held more than 9,000 people Monday night, nearly double its intended capacity of about 5,000. Some evacuees had to sleep in chairs, on piles of belongings, or on sheets of cardboard the floor. 

Evacuees take shelter at the George R. Brown Convention Center in Houston, Aug. 28, 2017.

Malachia Medrano, 2, sleeps at the George R. Brown Convention Center in Houston, the city's biggest shelter for evacuees escaping the floodwaters from Harvey, Aug. 29, 2017.

People wait to check into a shelter in the George R. Brown Convention Center during the aftermath of Hurricane Harvey on Aug. 28, 2017.

Flood victims receive food at a shelter in the George R. Brown Convention Center during the aftermath of Hurricane Harvey on Aug. 28, 2017 in Houston, Texas. 

Volunteers with The American Red Cross register evacuees at the George R. Brown Convention Center in Houston on Aug. 28, 2017, after Hurricane Harvey inundated the Texas Gulf Coast. 

Charles Maltbie of the American Red Cross told CBS News, "The assumptions that were in place, even a week ago when we were setting this up, have just been completely overwhelmed." But he said it's going "as well as it can be with the conditions." 

Volunteers sort through donated clothing at a shelter in the George R. Brown Convention Center during the aftermath of Hurricane Harvey on Aug. 28, 2017 in Houston, Texas.

A man checks on his cat in a cage at the shelter set up in Houston's George R. Brown Convention Center after Hurricane Harvey, Aug. 28, 2017.

A man steps outside for a cigarette after taking shelter in Houston's George R. Brown Convention Center during the aftermath of Hurricane Harvey, Aug. 28, 2017.

Charlotte Mills reads her Bible in the warehouse at Gallery Furniture in Houston, which opened its doors as a shelter after Hurricane Harvey, Aug. 29, 2017.

Flood victims eat and rest at a shelter in the George R. Brown Convention Center during the aftermath of Hurricane Harvey on Aug. 28, 2017 in Houston, Texas. 

Edward Jones, 11, holds his step-brother Mickel Duane Batts at the Lakewood Church in Houston, Aug. 29, 2017. Pastor Joel Olsteen and his congregation opened their church as a shelter for evacuees in the aftermath of Hurricane Harvey.

People wait to check into a shelter in the George R. Brown Convention Center during the aftermath of Hurricane Harvey on Aug. 28, 2017 in Houston, Texas. 

A man is patted down as he is processed into the shelter at Houston's George R. Brown Convention Center, Aug. 29, 2017. Police checked to make sure evacuees did not bring alcohol or weapons into the shelter.

"CBS This Morning" co-host Norah O'Donnell reports from amid a sea of cots at the emergency shelter in Houston's George R. Brown Convention Center.

A vet holds a dog at the shelter in the George R. Brown Convention Center in Houston, Aug. 28, 2017.

Evacuees get some rest in the warehouse at Gallery Furniture in Houston, which opened its doors to residents needing shelter, Aug. 29, 2017.

Jakobe Thomas plays with his sister Journey Thomas, 1, in the warehouse at Gallery Furniture in Houston, which was turned into an emergency shelter. The Thomas family stayed there after evacuating their flooded home over the weekend.

Flood victims are seen at a shelter in Houston's George R. Brown Convention Center, with a child's toy truck in the foreground.

A child is helped off the back of a rescue truck after his family's home was inundated with flooding from Hurricane Harvey on Aug. 28, 2017 in Houston, Texas. 

Evacuees are transported to the shelter set up at Houston's George R. Brown Convention Center after Hurricane Harvey inundated the Texas Gulf Coast, Aug. 27, 2017.

Flood victims gather for food at a shelter in the George R. Brown Convention Center in Houston, Aug. 28, 2017.

Evacuees carry their belongings to the shelter set up in Houston's George R. Brown Convention Center, where over 9,000 people took refuge after Hurricane Harvey, Aug. 29, 2017.

People check into a shelter with their pets at the George R. Brown Convention Center in Houston, Aug. 28, 2017.

Evacuees arrive at the Houston convention center shelter after evacuating from their homes with whatever they could carry, Aug. 28, 2017. 

"CBS This Morning" co-host Norah O'Donnell reports from the emergency shelter in the George R. Brown Convention Center in Houston, where volunteers are sorting through huge piles of donated clothing for flood victims.

Volunteers sort through donated clothing at Houston's George R. Brown Convention Center, where thousands of storm victims took shelter, Aug. 28, 2017. 

People sorting through donated clothing and household goods at the George R. Brown Convention Center in downtown Houston, the city's main evacuation center.

The George R. Brown Convention Center in downtown Houston, the city's main evacuation center, held more than 9,000 people Monday night, nearly double its intended capacity.

Evacuees are unloaded from the back of an open-bed truck at the George R. Brown Convention Center in Houston after Hurricane Harvey inundated the Texas Gulf Coast, Aug. 27, 2017.