BART has removed all four cars from an out-of-service train that derailed in Concord during the Friday evening commute, prompting buses and a shuttle train to stand in for normal train service between four stations on the Pittsburg/Bay Point line.

Cranes this morning hoisted the third of four cars involved in the derailment off of elevated BART tracks in Concord, agency spokesman Jim Allison said.

Flatbed trucks are bringing the cars to a BART maintenance yard. Crews will replace cables and other parts of the trackway damaged by the derailment and will inspect the rails for safety, the spokesman said.

Allison said the trackway sustained "significant" damage in the derailment, which happened as an out-of-service train was leaving the Concord station around 6:30 p.m. Friday.

No conductors were injured in the derailment.

BART officials continue to investigate what caused the derailment, which agency spokeswoman Alicia Trost said happened as the train traveled over a switching mechanism known as an interlocking.

Full repairs to the trackway aren't expected to be completed before this afternoon, according to Allison.

Until then, BART is running bus service between the Pleasant Hill and Pittsburg/Bay Point stations as well as a shuttle train between the Pittsburg/Bay Point and North Concord stations.

Those planning to take BART from Contra Costa County toward San Francisco today are encouraged to take trains to and from the Pleasant Hill station to avoid significant delays.

Allison said BART employees will be on hand at each of the four affected stations to answer travelers' questions today.