VALLEY CENTER ? Hundreds of people were evacuated in this Wichita-area town after an explosion Tuesday morning at a solvents plant ignited about 660,000 pounds of chemicals, authorities said.

Twelve people went to a Wichita hospital as a precaution, said Helen Thomas, a spokeswoman for Wesley Medical Center. Most were examined and released, and none was expected to be held at the hospital overnight, she said.

As health concerns eased, a mandatory evacuation of the 2-mile radius around the plant was canceled around 10:50 a.m.

“They are still testing the air quality,” said Amanda Matthews, a spokeswoman for Sedgwick County. “So far the reports we are getting back is it’s OK.”

Tuesday evening, Matthews said efforts to put out the fire have gone better than expected, with only one of the tanks still partially ablaze.

“We’re not out in the clear yet, but we’re seeing a light at the end of the tunnel,” she said.

The explosion at 9:15 a.m. at Barton Solvents in downtown Valley Center was followed by 15 or more blasts, touching off a fire that drew firefighters from several area departments. Big clouds of black smoke billowed from storage tanks, and flames were shooting up to 200 feet into the air.

Firefighters spent much of the day working to keep the blaze from spreading to other homes and businesses.

Sharon Watson, spokeswoman for the adjutant general’s office, said 60 Kansas National Guard troops were to start arriving Tuesday night in Valley Center to help local law enforcement with security and public safety over the next two or three days.