Indian prosecutors have blamed a company that renovated a suspension bridge for its collapse at the weekend in which more than 130 people were killed.

Contractors installed heavier flooring during work on the 150-year-old bridge in Morbi but did not replace a rusty main cable.

Police believe the structure snapped due to excess weight when it was crowded with visitors Sunday, plunging 135 people to their deaths in a river below.

Nine people linked to the Oreva group, a watch and e-bike manufacturing firm that had a contract to manage the bridge, have been arrested on manslaughter charges.

Oreva "hired contractors who were not qualified enough", public prosecutor Harshendu Panchal told reporters after a remand hearing late Tuesday.

"The main cable of the bridge was not changed during renovation," he said.

"The police also believe that the weight of the bridge increased due to the four-layer aluminum flooring done by the contractors, which may have resulted in the bridge collapse," he added.

The 230-meter-long structure, a major tourist attraction in the area, was only reopened last Wednesday after nearly seven months of renovations that are said to have cost 20 million rupees ($240,000).

Authorities in the western state of Gujarat say the proper safety certificates were not obtained before visitors were allowed to return. At least 47 of the victims were children.

Oreva had been awarded a 15-year contract by local authorities to operate and maintain the bridge but investigations have since found it had no prior experience on such projects.

However, Oreva group manager Deepak Parekh reportedly told the court: "It was the will of God that such an unfortunate incident happened."

He and another Oreva manager, along with two contractors, were remanded in police custody, while five ticket sellers and security guards for the bridge were sent to prison awaiting trial.

Even in a country where infrastructure is often dilapidated, the bridge disaster is one of the worst in decades and has triggered widespread condemnation and demands for accountability.

Prime Minister Narendra Modi visited the accident site on Tuesday and promised a "detailed and extensive inquiry to identify all aspects relating to the tragedy".

Flags were flown at half-mast in Gujarat on Wednesday and all official and entertainment events were canceled.