IPSWICH, Mass. (AP) – The discovery of a dangerous mosquito-borne virus on the North Shore prompted town officials here to notify thousands of residents and spray Ipswich with insecticide.

Trouble is, the alert was issued for the wrong town.

Ipswich officials were told by the state Monday night that eastern equine encephalitis was discovered in a mosquito in their town. They hired an automated phone notification service to alert residents and sprayed the entire town that night.

The next day, scientists at the state Department of Public Health realized they’d notified the wrong town.

The infected mosquito had actually been discovered 10 miles further north, in Amesbury.

The health department sent a two-page apology to Ipswich on Wednesday.

Dr. Alfred DeMaria, director of communicable disease control at the Department of Public Health, said an investigation found the person who entered the data had just finished logging information about Ipswich, where two mosquito pools recently tested positive for West Nile virus.

The employee then turned their attention to the Amesbury discovery, but forgot to change the name of the town on the screen and recorded the Eastern equine encephalitis discovery under Ipswich.

Meanwhile in Ipswich, the company hired to deliver the automated telephone message, Dialogic Communications of Tennessee, had its own computer problems.

“Some residents got as many as 15 calls and others did not get any message,” Ipswich Town Manager Robert Markel said.

About 4,000 households were reached before the warning system was shut down.

In Amesbury, townwide mosquito spraying was planned for Thursday after bad weather derailed plans to do it on Wednesday.