US grocery retailer Safeway is voluntarily recalling some green onions because they may be contaminated with salmonella.

The recalled green onions, also known as scallions, were sold from 3-7 August in Safeway and Pak 'n Save stores located in Northern California and Western Nevada.

The salmonella was detected through routine testing at the California Department of Food and Agriculture's Center for Analytical Chemistry.

"Safeway's first concern is the health and safety of our customers," said Frank Calfas, president, Safeway Northern California Division. "Though there are no reported cases of any illnesses, this voluntary recall is being done solely out of an abundance of caution."