One large boom shook Calistoga at about 12:30 p.m. Tuesday, marking the end of an old case of ether that had been stored for decades at the local fairgrounds.

"It was pretty big. Like building-shaking big," said Calistoga police Dispatcher Molly Harden of the blast.

Napa County's bomb squad exploded the gas at the fairgrounds, fearing the volatile gas would be too dangerous to move, sheriff's officials said.

County officials Tuesday morning had warned Calistoga residents of the pending blast through news releases and automated house calls.

Nine homes near the fairground reportedly were evacuated briefly.

The ether, in 96, ?-pound cannisters, was found Monday afternoon in a wooden crate.

Labeling on the box indicated it was packaged in March 1957 and officials speculated it could have been stored at the fairgrounds for more than 50 years.

Sheriff's officials reported the ether had been part of disaster supplies for a 200-bed hospital.

Harden said only four calls were made to the Calistoga Police Department of residents who were caught by surprise by the big boom.