SINGAPORE - Four coronavirus patients linked to a cluster at Bukit Panjang Integrated Transport Hub are all bus drivers, said transport operator SMRT on Sunday (July 26).

The cluster was first announced by the Ministry of Health (MOH) on Friday night.

According to SMRT, three of the drivers contracted Covid-19 in their households.

The last driver, a 28-year-old Malaysian work permit holder, was confirmed positive on Thursday.

MOH said on Friday that his infection was detected as part of the ministry's proactive case finding of individuals working at a newly emergent workplace cluster, adding that his results indicated that he was likely to have a past infection and was no longer infectious.

However, the worker showed symptoms on July 1 and subsequently went to work at Ulu Pandan Bus Depot and Bukit Panjang Integrated Transport Hub.

SMRT on Monday said that the driver reported sick for fever on July 1, and was then put on medical leave from July 1 to July 7. He returned to work on July 8, and was no longer symptomatic then.

All four drivers tested positive between July 7 and July 24, said SMRT.

They drove bus services 976, 184 and 176.

SMRT chief communications officer Margaret Teo said the company is closely monitoring the drivers' conditions and offering help to their families.

She added that SMRT's employees who were in close contact with the four have been placed on leave of absence.

A Land Transport Authority (LTA) spokesman also said SMRT is assisting MOH with contact-tracing, as well as disinfecting buses and common facilities.

As a precautionary measure, SMRT has closed off the canteen and staff lounge at the transport hub for thorough cleaning and disinfection, said the spokesman, who added that the risk of transmission from transient contact such as commuting on public transport is assessed to be low.

"We have also reiterated to all public transport operators the need to continue to enforce strict safe management measures for public transport workers which include spaced seating and staggered break times. If they are unwell, they should seek medical attention immediately and remain at home," said the spokesman.

LTA reiterated that all commuters are required to wear masks when taking public transport, and that they should also refrain from talking on public transport, practise good personal hygiene and avoid taking public transport if unwell.