Heavy rain has hit Maharashtra and Karnataka. (PTI)

The Mumbai-Bengaluru National Highway No 4, closed near Kolhapur in Maharashtra for the last six days, was opened for traffic on Monday after flood waters receded, an official said.

Thousands of trucks carrying essential commodities were stranded since last week on the flood-hit highway, which is a vital road link between Maharashtra and Karnataka.

Traffic movement was allowed on Monday morning between Kolhapur and Belgaum in Karnataka through one lane on either side of Shiroli bridge on the six-lane busy NH-4, Kolhapur's Superintendent of Police Abhinav Deshmukh told news agency PTI.

"Initially, the highway has been opened for heavy vehicles, especially those carrying essential commodities like grains, fuel, medicines and milk," he said.

"A portion of the highway is still submerged up to 1.5 feet under the flood waters, but we decided to allow heavy vehicles to ply as Kolhapur has been struggling to get the essential commodities," he added.

Heavy rain in western Maharashtra in the last one week caused flooding in several areas, with Kolhapur and Sangli districts being the worst hit.

A portion of the Mumbai-Bengaluru NH-4 was also submerged in water , forcing authorities to close it for traffic the first time last week.

The police also dismissed rumours that cracks have developed on the highway's bridge located on the Panchganga river.

"We have inspected the spot and it is not a crack but an expansion gap. Still, the National Highway Authority of India (NHAI) will carry out a structural audit before traffic is completely restored," Mr Deshmukh said.