A sinkhole has opened up in the middle of a busy main road, forcing the closure of a city-bound lane for an extended period.

The sinkhole on Kerford Road in Albert Park, Melbourne, was discovered just after lunchtime and measures about one and a half metres deep. However, authorities say the real concern lies beneath the surface.

While the hole appears small from above, its width underneath the road spans approximately 15 metres, creating a cave-like void beneath the busy thoroughfare.

Know the news with the 7NEWS app: Download today

South East Water experts have been brought in to investigate and repair the damage, with crews working to determine whether a sewer line below contributed to the collapse.

The road closure has tested the patience of some motorists, with one woman attempting to drive around the site on the footpath before being quickly stopped by police.

Road crews remained on site on Monday night as investigations continue into what caused the sinkhole to form.

Authorities are warning commuters to find alternative routes to work on Tuesday morning, as the city-bound lane will remain closed for some time.