Someone in the area pulled a gun and fired four to six shots, hitting a 17-year-old male student and a 17-year-old female student, both from the Washington area, Overton said.
Authorities offered no information on a possible motive.
The girl was taken to Christiana Hospital in Newark, Del., with a traumatic wound to the abdomen, said John Wilson, the deputy chief of Kent County Emergency Services. She was in serious condition.
The boy was taken to Kent General Hospital in Dover with an ankle wound. He is in stable condition, authorities said.
The Associated Press reported that the male student has refused to answer police questions about the incident, leading to speculation that he may have known his attacker, according to a federal law-enforcement official who spoke on condition of anonymity.
Authorities said they would not identify the students because of federal privacy laws.
The campus has been locked down today, classes are canceled and students are being kept inside. The school will reopen tomorrow on a limited basis, university president Allen Sessoms said.
Authorities said that students and employees were notified of the emergency via the university Web site, by phone and through notices posted in dormitories. Carlos Holmes, a spokesman for Delaware State, said the school had improved the speed of its notifications following the shootings in April at Virginia Tech.
"I'm satisified we did absolutely the best we could," he said.
But more than half of students live off campus, and some arrived at the 400-acre school knowing nothing of the shooting.
Commuter student Eduardo Rivera, 25, of Milford, said when he arrived at the closed campus, he was surprised by the throng of news media gathered outside the main gate, and figured it must be connected to an event at nearby Dover International Speedway.
"I thought it was about racing, or NASCAR, or something like that," he said. "I'm shocked. I don't expect to hear something like this when I'm trying to go to class."
Freshman Ryan Robinson, 18, said he was in his first-floor room in Conwell Hall dormitory, working on a paper about Darwinism, when he heard three shots. Robinson, of Bear, Del., said he immediately dropped to the floor, raising his head only after he noticed the glare of flashing red emergency lights.
Through the window, he saw that other students had gone outside of the dormitory and were carrying a male student, obviously injured, toward Evers Hall dormitory. He couldn't fully see the woman, Robinson said.
Authorities were on the scene almost immediately, he said. About 15 to 20 campus and state police officers began telling people to go back inside.
Today's lockdown occurred as Nascar racing fans flooded the area, their RVs and campers parked around the speedway. Racing officials issued a statement calling the shooting "isolated," and said it posed no threat to race patrons or schedules. The Nascar Nextel cup qualifying race was scheduled for 3:15 p.m. today, followed by the Sunoco 150 Nascar Busch East Series race at 4:45 p.m.
Only weeks ago, the college community held a memorial service for three students and an incoming student who were shot execution-style on Aug. 4 as they hung out at an elementary school in their hometown of Newark, N.J.
Natasha Aeriel, 19; her brother, Terrance Aeriel, 18, and Dashon Harvey, 20, were students. Iofemi Hightower, 20, had planned to attend Delaware State this fall. Natasha Aeriel, the only survivor, helped police identify six suspects who have been arrested.
"There was a shooting on my street, then I came to college and it follows me here," said student Okezie Omyeanuji, from Germantown. "You think Delaware is safe and quiet. This is ridiculous."
Delaware State is a historically African American university founded in 1890. It serves 3,278 undergraduates and 379 graduate students, less than half of whom live in college housing.
One student said some of her friends were near this morning's shooting when it started. "They were pretty shook up," said Samantha Williams, of Orange, N.J.
Campus police are leading the investigation, assisted by the Delaware State Police and agents from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.
Sabrina Allen, a Delaware State graduate who is athletic director at Girard College High School in Philadelphia, said she spoke with her nephew, Benjamin Bullock, a sophomore at the school.
He told her that "the security folks had the situation under control," she said. "Everybody is OK. They're not frantic. It's people on the outside who are worried."
Philadelphia Eagles football center Jamaal Jackson, who attended the school, said he heard about the shooting when he arrived at practice.
"There are still people there I care about, as far as coaches and some of the players," said Jackson, 27. "It's sad that something like that happens."
Asked if there were problems at the school when he attended, he said, "We'd have our occasional campus fights, but who doesn't? It never came to gunfire."
A school shooting can happen anywhere - just look at Virginia Tech, he said.
"It's sad and it's tough to swallow, he said. "Delaware State's been kind of on the rise as an athletic program. It's kind of hard to attract recruits to come there when something like this happens."
TV news trucks set up in what became a small media campound in the parking lot of a Best Buy store across from the main gates of the school.
Restaurateur Joe Horres, 58, passed out bottles of water and boxes of Chick-Fil-A chicken.
"You're just doing your job," he said, "and I'm just doing mine, promoting Chick-Fil-A."
"And feeding hungry people," added his 17-year-old daughter, Katherine Lykens.
Staff writers Samantha Shepard, Dan Hardy and Gary Miles contributed to this story.
Contact staff writer Jeff Gammage at 610-313-8110 or firstname.lastname@example.org.