Fresh tomatoes and lettuce have emerged as a key suspect in an 18-state outbreak of salmonella that has sickened 172 people, including eight in New Hampshire, public health officials said yesterday.

Seven of the eight New Hampshire residents had eaten fresh tomatoes, said Gregory P. Moore, spokesman for the New Hampshire Department of Health and Human Services. But Moore stressed that an investigation is continuing, and in the meantime people should take precautions when eating meat, eggs and fresh produce of all kinds.

"That (tomatoes) is a suspect, but we can’t say with any surety that that’s the source," Moore said. National health officials said lettuce was a key suspect along with tomatoes.