State health officials are warning residents to stay indoors, close all windows and shut off air conditioners in 21 southeastern Massachusetts communities scheduled for aerial pesticide spraying against mosquitoes tonight and tomorrow evening. The spraying comes after health officials detected Eastern Equine Encephalitis samples in mosquitos in the region, the Massachusetts Department of Public Health said this evening.

The following communities will be sprayed with pesticides starting at 8:15 p.m. tonight through 2 a.m.: Acushnet, Berkley, Bridgewater, Carver, Dighton, East Bridgewater, Easton, Freetown, Halifax, Hanson, Kingston, Lakeville, Middleborough, Norton, Pembroke, Plympton, Raynham, Rehoboth, Rochester, Taunton, and West Bridgewater. A second round of spraying is scheduled for Saturday evening from 8:15 p.m. through 2 a.m.

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The safety recommendations apply to residents of the affected communities, and those who live within 1,500 feet of the border of those communities, said the Department of Public Health in a statement. Only air conditioners with a fresh air intake function should be switched off during the hours of the spraying.

Health officials also warned that fish ponds should be covered overnight, pets should be kept indoors to reduce exposure, and all food that comes from a home garden should be rinsed thoroughly.

Although there have been no human cases of the West Nile virus or EEE this year, “two EEE-positive mammal-biting mosquito pools in the town of Rehoboth” were detected, the department said this evening. This bumped the EEE threat level to “High” in Rehoboth, and “Moderate” in Attleboro, Seekonk, and Swansea.

The aerial spraying of the pesticides is extremely dependant on weather conditions, and can be postponed last minute, the department statement said. Residents or nearby residents can check www.mass.gov/dph for updates.