FLINT, MI -- The city says there's been too much disinfection byproduct in Flint's water system recently, something that -- over many years could cause liver, kidney or central nervous system problems and an increased risk of cancer.

The notice from the city says Flint water is safe to drink but warns those with "a severely compromised immune system, (who) have an infant or are elderly" that they "may be at increased risk and should seek advice about drinking water from your health care provider."

For others, there is no need to boil water or take other actions, the notice says.

"It 's been a rocky road," City Council President Josh Freeman said. "It's not acceptable.

"People have a reasonable expectation that they are going to have quality drinking water. This is obviously going to rattle people."

Mailed Friday, Jan. 2, the customer notices come after the state Department of Environmental Quality issued a notice of violation of the Safe Drinking Water Act for maximum contaminant levels for trihalomethanes -- or TTHM -- a group of four chemicals that are formed as a byproduct of disinfecting water.

As city water plant operators used additional chlorine to fight bacteria in the Flint water system this summer, disinfectant byproduct levels also likely increased, city officials said Friday.

Levels of TTHM have decreased since that time, and in Nov. 20, testing at eight locations showed only one that exceeded maximum contamination levels, according to the state's notice of violation.

Testing on Aug. 21 showed contaminant levels were higher than maximum levels allowed at each of the same eight locations.

"The water in our system today is not in violation" because of efforts to improve the distribution system and adjust water treatment, said Doughtery Johnson, utilities administrator at the Flint water treatment plant.

Those changes "have likely contributed in part to the reduction in TTHM levels reported in the most recent quarter, and suggest the city may be able to achieve compliance with the TTHM standard," the state's violation notice says.

City officials released a statement Friday saying its actions "appear to have corrected ... known compliance issues with the system, including a recent temporary increase in the maximum contamination level (MCL) of trihalomethanes (TTHM)

"Both the city of Flint and the MDEQ expect the corrective measures being implemented will resolve the issue by early 2015," the statement says.

The city's recent violation for excessive disinfectant byproducts is the latest in a series of issues for the Flint water system since officials changed the water source pumped to homes and business from treated Lake Huron water purchased from the city of Detroit to water drawn directly from the Flint River and treated in Flint.

The use of Flint River water is expected to be temporary because the city is a partner in the Karegnondi Water Authority, which is building a new water pipeline to Lake Huron.

Once that system is put into service, something that's expected to happen by the end of 2016, Flint will be in a position to return to using lake water.

Freeman said that long-term plan remains "the right path to be on" and said the city appears to be on course to fix the problem of disinfection byproduct levels, but Councilman Eric Mays called on the City Council to hold an inquiry about drinking water quality.

"Sworn information given under oath is the only information I trust," Mays said.

Residents have complained to the council about the smell and taste of the water since Flint stopped the flow of lake water here and there were three boil water advisories in a 22-day span this summer after positive tests for total coliform and fecal coliform bacteria.

In October, General Motors announced that it would no longer use treated river water at its engine plant here because of fears high chloride levels would cause corrosion.

Flint Department of Public Works Director Howard Croft said that the city's aging water distribution system remains the biggest obstacle to meeting Safe Drinking Water standards but officials have also said the relatively low quality of untreated river water and the need to more carefully manage chemical treatment has also been a factor.

Croft told a City Council committee in September that river water has proven hard to treat and to keep safe because of variables that wouldn't be factors in lake water, like temperature fluctuation and rain.

But Croft said the city has made improvements to its distribution system and said additional improvements are on the way, including pipe replacements, leak detection and hydraulic monitoring.

Johnson said the size of Flint's water system, which once served more than 200,000 people and now serves about half that number, also makes keeping water fresh in distribution pipes difficult.

Stagnant water is more susceptible to contamination, officials have said.

Flint will remain in violation of the Safe Drinking Water Act until every test site in the city has acceptable levels of disinfectant byproducts, Johnson and Croft said.

The next round of testing is scheduled to take place in February.