A busy part of Melbourne's north-west, which was closed off for more than two hours as a bomb squad robot investigated a bus, has now been declared safe.

An area around Kellaway Avenue and Mount Alexander Road at Moonee Ponds, not far from the main shopping precinct, was closed to the public for much of the afternoon.

A number of armoured specialist police officers have been investigating the bus. ( AAP: Julian Smith )

Police had closed Mount Alexander Rd in both directions, causing heavy traffic.

A bomb squad robot was sent into the area and onto a bus parked along Kellaway Ave, near the Moonee Valley Council headquarters, local library, police station and popular Queens Park.

A police spokeswoman said police had now declared the area safe.

A council office on Kellaway Ave was closed as police investigated but staff were not evacuated, a spokeswoman said.

The Metropolitan Fire Brigade was also on scene.