Key Points:

Hundreds of Auckland rail passengers were late home last night after smoke forced the evacuation of the Britomart underground station.

Some gave up and caught buses or car-rides with friends as services on all three suburban railway lines were disrupted for several hours after the smoke alert about 4.15pm, which brought firefighters scrambling and prompted the evacuation of about 150 people.

Veolia Transport spokeswoman Tessa Marjoram said it appeared brakes on a locomotive hauling a refurbished SA passenger train into the station were giving off excess smoke, although the cause was still being investigated.

Although the all-clear for passengers to re-enter the station came just before 5pm, the disruption had a cascading effect throughout Auckland's rail network, causing half-hour delays to all services for two more hours.

Passengers milling about the platform complained about a lack of information from train officials about departure times, and misleading bulletin boards.

Guards had to deter some from boarding a Pukekohe train after the passengers were wrongly advised by an overhead display that it was bound for Waitakere.

Britomart is a rare example internationally of an underground station for diesel trains and, although it has strong extractor fans, there have been complaints about fumes.