Federal inspectors looking into the cause of the May derailment and collision of two Metro-North commuter trains in Bridgeport and a second accident in which a rail worker was struck and killed in West Haven, released a preliminary agenda Tuesday for a hearing into the matters next month.

More than 20 representatives from Metro-North, government, industry and rail workers are expected to testify on four different topic areas over the two-day hearing beginning Oct. 22. The four topic areas being addressed are: track maintenance and inspection; railroad passenger car crashworthiness; operational protection of on-track work areas; and the organizational safety culture.

The hearings will be held at NTSB headquarters in Washington, D.C., and will also be available via webcast.

The May 17 derailment injured more than 76 people when a train heading to New Haven derailed during a busy Friday evening rush-hour commute. About 30 seconds after coming to a halt, it was struck by a westbound train. There were about 250 passengers on each train at the time of the accident.

A preliminary report from the NTSB cited an inspection of the piece of track done by Metro-North two days before the crash that found that crushed stone and other material under an insulated rail joint moved out of alignment when it was traveled over. The NTSB report did not offer information on whether Metro-North addressed the condition between the May 15 inspection and the accident two days later.

The NTSB has taken sections of broken rail that had been secured by rail joint bars to its Washington metallurgy lab for examination.

U.S. Sens. Richard Blumenthal and Chris Murphy have asked NTSB Chairwoman Deborah Hersman to expedite the investigation and release more information as soon as possible.

The equipment damage was estimated by Metro-North to be at least $18 million, including repairs to re-establish service five days after the derailment.

Two passengers, a Stonington woman and a Milford man, have filed lawsuits seeking damages for injuries.