The most intense damage was at two schools that were reduced to piles of rubble.
At Plaza Towers Elementary, at least seven students lost their lives. Mr. Lamb told CNN that several of them drowned in the basement, where they sought shelter.
Rescue teams found several children buried in nearly 40 feet of debris, CNN reported, and searches continued as darkness fell Tuesday.
All the children at Briarwood Elementary seem to have survived.
Faced with another national tragedy involving elementary school children, President Obama comforted grieving families and pledged that the federal government would assist in any way it can.
“Our prayers are with the people of Oklahoma today,” he said during remarks in the East Room of the White House, “and the teachers who shielded their students and all of those who, when darkness fell, searched for survivors throughout the night. The people of Moore should know their country will remain on the ground, there for them, beside them as long as it takes for their homes and schools to rebuild.”
It was similar to the message Mr. Obama delivered to the people of Joplin two years ago after storms nearly wiped the Missouri city off the map.
Even as Joplin continues to rebuild, city leaders are offering their help to Moore.
Joplin announced that it was sending a team of public safety employees, including about a dozen police officers and firefighters, to assist with rescue and eventual cleanup efforts.
“We remember the amount of assistance that we received following the tornado two years ago, and we want to help others as they helped us,” said Joplin City Manager Mark Rohr. “We feel an obligation to serve them as they have served us.”
Similar kindness, along with attempts to provide normalcy and comfort, were seen across Moore on Tuesday.
Outgoing Moore Public Schools Superintendent Susan Pierce said that, despite the horror, all three local high schools will hold graduation ceremonies as scheduled Saturday.
State Rep. Mark McBride offered a heartfelt invitation at an afternoon news conference.
“I just want to let people know, call me if you need anything. If you need a bottle of water, if you need a case of water, if you need a place to stay, you can come to my house,” he said just before announcing his cellphone number on live national television.
• Susan Crabtree and David Sherfinski contributed to this report.