American Canyon has been cited for violating the state's drinking water quality standards.

Coliform bacteria were found in the city's drinking water system May 9 and May 23, American Canyon and state officials said Thursday.

The water contamination did not pose a significant health hazard, though the presence of coliform bacteria can cause gastrointestinal problems, said Bruce Burton, district engineer for the California Department of Health Services, the state agency that cited American Canyon May 31. Coliform bacteria are commonly found in the environment, he said.

The water samples taken in May did not contain E. coli, Burton also said, referring to the fecal bacteria that can cause serious illnesses, even resulting in death.

The water samples that tested positive for coliform bacteria came from two locations along the city's 85-mile long water distribution system.

American Canyon Public Works Director Robert Weil said one water sample was taken May 9 near a business at 100 Napa Junction Road; the other was taken May 23 near a mobile home park at 260 American Canyon Road.

The American Mobile Home Park is home to 200 trailers, according to the city's public works department.

The contaminated water may have entered the system when the water mains were shut down because of construction in May, according to Weil and Steven Moore, the city's water systems manager.

Under state law, the city has until June 14 to issue public notices, according to the citation.

Burton, who has worked for the Department of Health Services for 20 years, could not recall the last time when the city was cited for violating the state's drinking water quality standards.

The city's water system is very good, Burton also said, adding he drinks the city's water when he is in American Canyon.

The city has had other water problems in the past. The Environmental Protection Agency reported finding elevated levels of Trihalomethane, a colorless, odorless chemical in the water system in 2005. Weil said in November that THM had returned to normal levels by November.