Updated

Federal investigators are trying to determine if excess speed may have caused the commuter train derailment that killed two passengers and injured more than 80 others, the acting chairman of the National Transportation Safety Board (search) said Sunday.

Mark Rosenker said investigators are examining three data recorders recovered from the locomotive and cars to determine if the train was traveling faster than the speed limit when it switched tracks at a crossover just before it derailed Saturday.

"The train should have been doing 10 mph when it hit that crossover; that's the rule," Rosenker told The Associated Press. "We will get an exact speed when we ... see what the data recorders are telling us."

He said investigators expected to determine the train's speed by Sunday evening. On Saturday, railroad officials had said the speed limit was 15 mph.

Seventeen of the injured passengers remained in "severe or serious condition," Rosenker said Sunday.

Rosenker said investigators also would analyze the tracks, the train's maintenance history, records of the train signals, toxicology reports on the crew and other factors.

The double-decked commuter train was headed into Chicago from Joliet (search) on Saturday morning with 185 passengers and four crew members when its locomotive and five rail cars jumped the tracks about 5 miles south of downtown.

The train and the track had just been inspected Friday, said Judy Pardonnet, a spokeswoman for Metra (search), the commuter rail system that services the Chicago area.

The train engineer, three crew members and dispatchers were all tested for drugs and alcohol, which is standard procedure, Pardonnet said. The engineer had been on the job for 45 days after completing Metra's six-month training program, which included at least some training along the route where the derailment occurred. He also worked for more than five years as a CSX Corp. (search) freight train engineer.

A similar derailment occurred on the same stretch of track in 2003, injuring about 45 people. A preliminary NTSB (search) report found that the train was going almost 70 mph at the location where it was supposed to switch from one track to the other.

Pardonnet said the two derailments may have been just a coincidence. "I don't think it's anything specific to this area, but it's still under investigation," she said.

A 22-year-old woman died on the train Saturday and a 30-year-old woman died at a hospital, said Pardonnet.

The women were the first people killed in a derailment in the history of Metra.