Rail operator SMRT has come out to assure the public that its trains do not contain asbestos, a material that is highly hazardous to health and is banned in Singapore.

The company was responding to queries from The Straits Times about a statement it sent to one of several commuters who had complained about a burning smell on trains and station platforms. In the statement, SMRT said its new trains use "composite brake blocks made of fibre asbestos with metallic grains".

The explanation, shared on Facebook by commuter Alvin Lee, said the brakes give off "a strong smell" when heated. "This will gradually reduce as the brakes become seasoned over time," SMRT said, adding that the smell does not pose any health risk.

SMRT later clarified that this statement had been a mistake, but not before it had caused some concern.

When contacted, the National Environment Agency said the importation of asbestos and products containing it has been prohibited here since the late-1980s.

Asbestos fibre can be inhaled and carried into deep recesses of the lung, where it can cause fibrotic lung disease. It can also cause lung cancer.

Several metro operators around the world have removed or are removing asbestos-lined brakes from their trains. A check with SBS Transit - the other rail operator in Singapore - revealed that none of its trains contain asbestos.

Dr Tan Shian Ming, a 39-year-old doctor who commutes by MRT, said: "It is not safe to be exposed to asbestos. I'm worried, and I hope that there will be some clarity from SMRT."

Another commuter, Betty Tan, a 50-year-old housewife, said she detects the burning smell on both the North-South and East-West lines. "I've been noticing it since last year," she said. "It smells quite toxic, and makes me want to get out of the station immediately."

In a clarification sent eight hours after The Straits Times asked about its asbestos statement, SMRT said it had all been a mistake.

Chief commuter engagement officer Elaine Koh said: "We assure commuters that asbestos is not used in any part of our MRT network.

"It was a human error caused by one of our customer relations staff putting his own words and sending the e-mail reply to a commuter too quickly... We are sorry for the unnecessary alarm caused."

Ms Koh added that MRT trains come to a stop through friction-braking by the application of brake shoes directly onto the wheels of the train. Heat is generated as a result and a strong smell associated with high temperature may be given off occasionally.

"We are working with the Land Transport Authority on reducing such occurrences on the network," she added.