The mayors of more than four dozen U.S. cities, citing a deadly train wreck and chemical spill in South Carolina, asked the federal government Wednesday to let local governments know when railroad companies haul hazardous materials through town.

In a letter to Homeland Security Secretary Tom Ridge, the U.S. Conference of Mayors asked "that you take immediate action with the freight railroads" to improve notice of hazardous material transported through cities.

A Homeland Security spokeswoman was unavailable, but Ridge said he would put the issue on the agency agenda, Augusta, Ga., Mayor Bob Young said.

Young met with Ridge briefly before Ridge addressed the mayors conference in Washington.

"We need to know what is coming, where it is going and when it is coming," Young said. "These trains run right through our neighborhoods and business districts."

The letter comes after the wreck of a Norfolk Southern train that killed nine people when chlorine leaked from a tanker car. The leak is the nation's worst from a train wreck since 1978.

The nearly 50 mayors signing the letter included Columbia's Bob Coble, as well as Baltimore's Martin O'Malley, Chicago's Richard Daley and Miami's Manny Diaz, conference spokeswoman Elena Temple said.

The letter was delivered Wednesday to Ridge and U.S. Transportation Secretary Norman Mineta, she said.

Knowing what materials come through town would allow fire and rescue units to launch rescue efforts more quickly and more safely, instead of first trying to figure out what chemicals are on wrecked trains, proponents say.

"We need a national notification system that would be another tool for our first responders," Coble said. "It just makes sense."

In the Graniteville wreck, some rescue personnel have said it took time to decide how to respond to the leaking train car. Key government warning systems to notify the general public weren't activated for hours after the crash.

Requiring notice of hazardous materials shipments would likely meet opposition from railroads. Norfolk Southern, for instance, would find it difficult to notify cities, company spokeswoman Susan Terpay said. Her company serves 22 states in the East, she said.