As the federal government continues to study a controversial gas drilling technique and the states tinker with their own regulations, some cities and towns are trying to halt local drilling. Philadelphia became the latest to do that on Thursday, when city officials called for at least a temporary ban on new wells in the watershed that serves the city's taps.

The request was part of a set of recommendations in a report approved by the city council asking federal and state authorities to tighten drilling regulations. The report also urges the city-owned utility to avoid buying gas that comes from the Marcellus Shale, the layer of rock that stretches under much of Pennsylvania and is considered one of the world's largest gas fields.

But the vote was largely symbolic. The utility doesn't buy any Marcellus Shale gas and has no plans to -- and new drilling in the Delaware River Basin is already on hold. The idea was to send a message, said Michelle Wilson, a spokeswoman for Curtis Jones, Jr., the councilman who sponsored the report.

"Philadelphia is a major city and we're hoping that behind this push, that we can use it for leverage," Wilson said.

The report cites the uncertainty around the environmental and economic impact of hydraulic fracturing—in which drillers use millions of gallons of water mixed with sand and chemicals to extract gas—to argue for a cautious approach to drilling. The Delaware River Basin Commission, the interstate authority that must authorize drilling permits in the watershed, has already suspended approving new wells until it adopts a set of regulations covering gas drilling. That process will take months, said a spokeswoman for the commission. The city council asked that the ban be extended until an EPA study of hydraulic fracturing is completed, which isn't expected until next year.

With the vote, Philadelphia joined New York City and Pittsburgh, as well as a number of smaller towns in the northeast and Texas, in trying to influence where and how the gas industry drills its wells.

In November of 2010 Pittsburgh became the first Pennsylvania city to ban drilling within its boundaries. The ordinance was written by an advocacy group called the Community Environmental Legal Defense Fund, which is pushing similar laws in municipalities throughout the Marcellus Shale region, including one in Maryland. Ben Price, who is organizing the effort for the defense fund, said the ordinances aim to protect residents' rights to clean air and clean water. He said cities and towns are simply stepping in where state governments refuse to.

But there's some question as to whether the outright bans by Pennsylvania municipalities are legal or whether state law supersedes them, said Travis Windle, a spokesman for the gas industry group the Marcellus Shale Coalition. Some towns have reportedly backed off proposing bans for fear of attracting costly lawsuits.

Windle said the local efforts are based on misinformation and will hurt economic growth.

"I think that just underscores what a huge job we have to do in better educating folks across the spectrum," he said.

While their direct impact on drilling is arguable, the various initiatives signal rising awareness and concern about drilling for natural gas, said Amy Mall, a policy analyst with the Natural Resources Defense Council, an environmental group.

"Local elected officials are hearing the concern from their communities and that's a good thing," she said. "I think it reflects that we need to look at this industry nationally."

New York City officials issued their own call for a ban on drilling in the city's watershed in December 2009. As with Philadelphia, drilling there is already on hold until a state environmental impact study is finished. Wilson said that Philadelphia officials have been working with their peers in Pittsburgh and New York to try to coordinate their efforts against drilling.

Before the Philadelphia vote, there was some confusion about whether the city council could direct the utility company's gas purchases. State law requires utilities to seek the cheapest gas, which for now means a long-term contract for fuel coming mostly from the Gulf of Mexico. Initially, the council wanted to ban purchases of Marcellus gas, should they become the cheapest option. That language was softened to urge the utility to consider environmental concerns as well as price and to try to avoid Marcellus gas.