The Washington, D.C.-based Environmental Working Group said in its report that consumers do not get enough information to determine which water best for them.

Both groups said some bottled water brands include the same information required of tap water providers on either labels or company Web sites.

The GAO called for more research but said the FDA should start by requiring that bottled water labels tell consumers where to find out more.

Community water systems must distribute annual reports about their water's source, contaminants and possible health concerns.

Consumers should know where all their water comes from, how it is treated and what is found in it, said Richard Wiles, senior vice president for policy and communications for the Environmental Working Group.

"If the municipal tap water systems can tell their customers this information, you would think that bottled water companies that charge 1,000 times more for this water could also let consumers know the same thing," he told The Associated Press.

The bottled water industry's trade group, the International Bottled Water Association, planned to testify Wednesday that the product, — subject to the same regulation as other soft drinks, teas, juices and other beverages — is safe. Additional standards apply for bottled water products labeled as "purified water" or "spring water," among other labels, because they must meet prove a connection to those sources, according to planned testimony from Joseph Doss, president and chief executive of the International Bottled Water Association.

Doss said consumers can learn about bottled water by contacting the company, reading its Web site and visiting sites run by state governments.

State safeguards for bottled water often exceed the federal, though they are less stringent than for tap water, the GAO wrote.

The trade group declined to comment on the reports before they are released.