"(Union Pacific officials) are trying to assure me that it's safe,' Molina said. "I said (the railroad) should put some order out to stop service on the tracks.'

A train derailed on Saturday in an unincorporated part of Los Angeles County near Pico Rivera, damaging two homes and causing the evacuation of 200 people.

In June 2003, a runaway train on the same line derailed in Commerce, destroying two homes and injuring 13 people.

The line starts in Los Angeles and runs east through Commerce, Montebello, Pico Rivera, unincorporated Whittier, Bassett and Industry.

Union Pacific spokesman Mark Davis said as soon as the line is determined to be safe by federal regulators, the railroad is legally bound to start running trains again.

Metrolink passenger trains resumed Monday, he said.

The wreckage and debris should be cleared from the area around the tracks in about two days, he said.

Repairs on the tracks would be completed soon after that and service will begin as soon as the railroad gets permission, he said.

Molina said, in the face of the two accidents, the Board of Supervisors at a meeting today will order a study of railroad safety in the county. She said she will ask that the study be finished in 15 days.

"I just can't take the railroad's word for it,' she said. "I have a responsibility to my constituents to find out what is going on.'

Molina was especially concerned about possible danger to Metrolink trains, which share the line with cargo trains.

Preliminary investigations show that the derailment was caused by a broken track rail, according to Davis.

The broken rail has been shipped to Washington D.C. to be examined by scientists and metallurgists from the National Transportation Safety Board (NTSB), he said.

Two calls to the NTSB were not returned.

Other area politicians called on federal lawmakers and the railroad to fund massive improvements to the area's rail system.

The Montebello City Council is working with federal legislators to get funding for a $165 million project that would lower into a trench train tracks that cut through the middle of the city.

The project would keep the train from having to cross traffic and would keep any derailments contained to the trench, he said. Two thirds of the line in Montebello runs through residential neighborhoods, he said.

"As farfetched as it seemed that a derailment would happened again, it did,' said Montebello City Councilman Bill Molinari , of the latest accident. "And there is no reason why it won't continue to happen. Something has to be done.'

Santa Fe Springs, Pico Rivera and La Mirada have also recently teamed up to lobby the federal government for more safety projects on a Burlington Northern Santa Fe Railroad line running through those cities.

Molina, Molinari and other politicians said the railroads should be paying for the safety improvements, not the taxpayers.

Davis said Union Pacific spends $1 billion a year on rail maintenance.

According to statistics from the Federal Railroad Administration, the nationwide number of derailments by Union Pacific trains has been decreasing the last five years.

Davis said Union Pacific was open to working with communities to improve lines, but noted that improvements take time and are very expensive.

In the long-run, many improvements will likely be necessary on most of the Los Angeles area's rail lines, experts say, especially due to increased train traffic from the Alameda Corridor Project.

The corridor project, which was completed in 2002, lowered 20 miles of train tracks in Los Angeles into a trench, which allowed trains to avoid cutting through crowded intersections.

Since the project's completion, train traffic through the area has increased by 30 percent, from an average of 33 daily trips in 2002 to an average of 43 this year, according to officials with the Alameda Corridor Transportation Authority.

So far, the corridor is only handling about half of its possible capacity, according to those officials.

Another funding agency, named the Alameda Corridor East, has a $900 million account to make improvements to area train lines, including the line on which the two crashes took place.

But many improvements are still months, or even years, off.

"For the time being, traffic is only going to get worse,' Molinari said.